If you write fantasy, one of the things you'll hear (probably over and over) is "magic should have a cost" (or, often, must have a cost). I saw it many times when I was looking at magic systems for my story, and I've seen it plenty of times on this forum too. While I don't necessarily disagree with the sentiment (it makes for an interesting story), it's become something that people parrot without any real comprehension, like "show don't tell", or that whole thing about dialogue tags. (Hint: for the first, it's not that important; for the second, as long as they're used in moderation, it's fine.)
What it all boils down to is "balance" - people think that magic is too powerful on its own, so they want to see a "cost" so that mages can't just up and take over the world, or deus-ex-machina their way out of everything. Of course, if your magic system is designed well enough and the story is written properly, this will never happen, but that's a topic for another post. What I want to discuss, here and now, is the concept of balance.
Which means, basically, that magic should have drawbacks. Not necessarily a "cost": the word "cost" brings to mind something the caster has to offer or risk to use their magic: sacrifices (blood, flesh, lives), side effects (this one's popular - pain, physical disfigurement, mental issues/brain damage, illness, etc.), death (by various means), backlash (the Wiccan's threefold rule), and on and on.
Drawbacks, however, are another form of "cost" that many people overlook. Time is a big one - if it takes ten minutes to cast a spell, that's a huge drawback - magic is severely limited in its use, if not its scope. Having to draw symbols and/or diagrams, chant words, use ingredients, make gestures or a series of movements (like a full-on dance); these are all costs. Having items that are expended upon casting the spell (not necessarily ingredients, but actual sources of the power) is also a good cost. The book Masks had an interesting concept: magic is a physical thing that bubbles up from underground like oil and can be mined or harvested; you have to have some to cast a spell, but once you do, it's gone (obviously, more power = more "magic" used up). If the caster has to make a pact with an otherworld being to gain power, that's a drawback (or a cost, either one) - only those powerful enough and/or crazy enough (depending on the being) will undergo the risk for the potential profit.
Public perception (mages are shunned, reviled, or outright outlawed) is another, though I don't recommend using it on its own unless it's a central part of the story. Similarly, you could use "time to learn magic" - it could take decades to master anything beyond the most basic spells, so very few bother (again, not a great example, but I threw it in here anyway).
A foil - some way that magic can be negated or otherwise circumvented - is also a drawback, though it's better used as a plot device. In the Wheel of Time, for example, Channelers could shield each other, cutting off your opponent from the source of their magic. There was also an herb called forkroot which, when ingested, prevented use of magic for a length of time. In the Avatar TV series, benders could be prevented from using their magic by surrounding them in elements besides their own - drop a firebender in an ice cave, suspend an earthbender in a wooden cage in the air, etc., and they're useless.
Basically, what you're looking for is something that will make your story interesting. Look at your world and your magic system - what makes sense as a drawback, given the world's history and the way magic works? What would make for a good plot and situations where your hero - assuming (s)he's a mage - will have to struggle to proceed, or may even fail outri\ght? Answer those questions, and you're on your way to making a unique magic system.
Since my characters are going to be travelling to various nations, I did some research on coins and currency. Coinage is one of those things that seems really minor, but it's the minor details that more verisimilitude. There's an amazing variance in the kinds of coinage used throughout history. The first coins were created in the 7th and 6th centuries BCE in Greece, India, and China (aka, the earliest civilizations). China even had https://en.wikipedia.org/wiki/Jiaozi_(currency) paper money about a thousand years ago.
Coins can take a surprising number of forms. The most ubiquitous is, of course, the round coin, but we also have square (in modern times, they have rounded edges for vending machines), 8/10/12-sided, and oval (common in the Orient). The edges can be milled, scalloped, or notched, to prevent clipping. Oriental coins often have holes or squares punched out of the middle to permit them to be strung on a lanyard. Coins are always stamped with some sort of design - often it's the likeness of the ruler who commissioned them, or a god/goddess; other common themes are animals, landmarks, or simple designs, often with a legend (writing, often a phrase of some sort).
90% of coins you seen in fantasy novels are copper, silver, gold, and (rarely) platinum. While these were in use in the real world, there were also a variety of other metals used: electrum (a naturally-occurring silver/gold alloy; rare), cupronickel (a copper/nickel alloy, sometimes used to debase silver coins), iron, lead, nickel (used since ancient times), brass (the Romans), and bronze (not that common, surprisingly). Your world could have other materials that are more or less common or valuable. Just keep in mind that we used softer metals for a reason - they're easier to stamp. It just so happens that many of them were also precious metals.
Cultures don't always rely on coinage as currency; many use livestock (chickens, goats, horses, cows), random silver items, https://en.wikipedia.org/wiki/Hacksilver, https://en.wikipedia.org/wiki/Knife_money knives (ancient China), food (salt, cocoa beans, or cheese), or other odd items. Cultures for whom metallurgy is impractical or impossible (undersea races, or those who live in a metal-poor world like Dark Sun) could use tokens of ceramic or bone, or beads of precious/semi-precious gemstones (agate, garnet, jade, pearls, coral, etc.), which could be pierced so as to be strung on a line.
And finally... denominations. Most nations have a base amount (like the Dollar or Euro), which they can then subdivide into smaller units (as coinage) and multiply into larger units (as larger bills or, rarely, also coinage). Coinage typically appears as one or more of the following:
1/100, 1/20, 1/10, 1/5, 1/4, 1/2.
So, for example, you could have the gold Mark as the base currency, then copper (at 1/100 mark), bronze (1/10), silver (1/2), etc. Or you could switch it up and have 20 coppers to the bronze, 15 bronze to the silver, and 3 silver to the gold. It's all up to you.
* https://en.wikipedia.org/wiki/Coin Wikipedia entry on coins. A central page where you can check out all the currencies of the world.
* http://listverse.com/2013/06/21/10-strange-forms-of-ancient-currency-2/ 10 Strange Forms of Ancient Currency
Everyone loves a good mystery. I'm not talking about the classic whodunnit, but the less common mysteries you find in fantasy worlds - the abandoned city, the ancient statues, the strange carvings lining the face of a cliff in the middle of nowhere. Who made them, when, and why? This is something that's often overlooked in fantasy stories.
Take our world, for example. Angkor Wat, the Nazca Lines, Macchu Picchu, the Cahokia Mounds, the Easter Island moai, Stonehenge... all of these are remnants of previous cultures and civilizations that left their mark. In some cases, we don't know who made them, how, or why, but they continue to excite our imagination. On the less tangible side, you have the myths and legends. Did you know that almost every culture on Earth has some variation of the Flood myth?
Sadly, many fantasy worlds are lacking in this respect. Sure, they might have long, detailed timelines with thousands of years of history, but they lack the evidence of all that history. Low fantasy is rife with them: Robert E. Howard's Conan series is a great example of ancient cultures - you can't walk ten miles without tripping over an abandoned ruin, old statue, or a tomb. Martin's Song of Ice and Fire also features lots of things that will never apepar in the books, or be explained - there's an entire continent (Sothoros) that is largely unexplored and has abandoned cities, old ruins, and strange creatures. Another way to go is Jordan's Wheel of Time series: back in the Age of Legends, people had much more advanced technology, the knowledge of which was lost during the war; now all that exist are scattered examples like the Tower of Genji, the Choedan Kal, and mentions of ancient wonders.
Of course, doing this is something like walking a tightrope. Look at the TV show Lost: it's rather infamous for tossing all kinds of random phenomena into the show, but in the end most of it was either poorly justified, or not explained at all. (FYI: "Magic!" is not an adequate explanation.) On the other hand, a good magician never reveals all his secrets: keep a few things hidden behind the curtain, and leave the readers always wanting more.
So you've created a world and populated it with various cultures. You've probably already decided long before now whether or not to add non-human races, and which ones they'll be, so let's take a moment to think this over. In the 80s and 90s, it seemed like elves, dwarves, orcs and such were pretty much required to appear in any fantasy world, thanks to the influences of D&D and similar RPGs. In the last 10 years or so, though, fantasy is becoming more human-centric, with the other races appearing less and less frequently. This can be a good thing - in the sea of human-centric worlds, one with multiple races will stand out. It's just a matter of whether or not readers will show interest in it.
Does the world really need non-humans? I.e., are you including them just because you think they're necessary, or do they serve a purpose? I'm not talking a purpose like allegory or metaphor, although those are fine. What I mean is, do they fill a niche? Nearly every creature on Earth today is here because it fulfills a role - from the smallest bacterium to the largest whale, they've evolved over millions of years to be where they are, and those whose roles are no longer important or who can't adapt go extinct.
Where did they come from? This is a huge question, and one that is often ignored. Granted, it doesn't usually have a bearing on the story, but it can shape a race's history - how it interacts with other races, its myths and culture, and even how members view themselves. Did they evolve from some lower life form, like humans did from the apes? If not, you should know how and why they came about. Did the gods put them down on the earth, fully-formed? Did they come through a portal to this world from another? Were they created by another race, or a single being?
How do they interact with other races? Are they open and welcoming, interbreeding with others (more on this later), or closed and xenophobic, attacking outsiders? Are they territorial, nomadic, content to settle in other races' lands, or something else entirely?
There are a lot more, like actual biology, but let's stick with this for now. In Earth's prehistory, there were dozens of different species of humans, most of which interacted with each other in some form - some were wiped out by competing races (either deliberately or through communicable diseases), and others died out because they were less adaptable, or because of environmental factors (climate change). And yes, there is evidence that our ancestors interbred - I'm sure you've heard that most non-African humans carry 1-4% Neanderthal DNA; scholars also agree that we interbred with the Denisovans, a group that lived in what is now middle Asia (Pakistan, up into Siberia), and another, as-yet-unknown group. So: Any time two races or cultures come into contact, they'll interact; if their biology is compatible, they'll mate, and if the genetics are close enough, they'll produce offspring. Which, of course, begs the question:
Are humans and these races in your world genetically compatible? If so, what do their offspring look like, what abilities (if any) do they have, are they sterile, and how do their parent races view them? How common are they, and where do they live (this leads back to how they're viewed/treated by their parent races)? Aside from RPG worlds, half-breeds, crossbreeds, and hybrids are seldom mentioned or dealt with. Sure, you could just say "they're all incompatible"; that's great, as long as you know *why*.
For the love of all that's holy, if you're going to add new races, please don't use the same tired old tropes. Elves, dwarves, orcs, gnomes... boooring. Give us something new - a race of lizard-like beings that live in the swamps; sentient spiders that inhabit the deep forest reaches; aquatic fish-men or cetaceans living in the oceans. Don't limit yourself to humanoids: dolphins and whales are generally accepted to be nearly as smart as humans (if not more so), and you're creating a fantasy world - the sky's the limit. If you really must use one of the tropes, give it a new spin - cannibal elves, desert dwarves, swamp orcs... or combine attributes of two or more races into something new. Be original. Have fun with it, as long as it all makes sense in the end.
What's in a name? Quite a lot, actually. You probably know the saying "the clothing makes the man"... well, it's the same with names. Unlike real people, characters can get any name you wish to give them, so you should make the effort to give them something that fits - both the person and the story. You don't want to call your fantasy knight Joebob Bumblethorpe III, unless you're writing a parody, in which case it's perfect.
As I mentioned before, I write fantasy, and it's tough for me to come up with names. I kept a list of them, back when I wrote stories in my first world - people, towns, inns, etc. - for when I needed them. They were all right, but they lacked character. If you want to evince a certain culture, a time, a feel for your story, your names need character. Even if you think it doesn't matter, it does. Every world, every city, every setting, no matter where it is, is unique and should have its own names.
For people like me, random name generators are a godsend. YMMV, of course; some people prefer to do their own heavy lifting, and that's great - I tip my hat to you, who are creative enough to do that. My absolute favorite is fantasynamegenerators.com. Over 900 gens, everything from real-world names to fantasy and sci-fi; people, places, things, groups, and even some description generators - you name it, it's either there or in the queue to be made. It takes a huge load off to be able to flip through a few pages of names and pick something you like (and possibly modifying it), rather than have to take the time to think up something yourself. (As a side note, Emily, the site owner, is a really nice lady - if you go over there, drop her a line and say hi - she loves to hear from the people who use her site.)
The great thing about such a huge variety (besides the huge variety, of course) is that you can mix and match names and cultures and races with a lot less effort. Let's take my world, for instance: one of my races, the Vargrim, use dwarven names for their cities, but I use Mongolian names for their people - as it turns out, Mongolian and FNG's dwarven have a lot in common, as far as construction. Both languages work really well because the Vargrim are sonorous - they have large chests, deep voices, and are excellent singers, so their language is rich with deep sounds, long vowels, and rolling consonants.
Likewise, the Ma'jaat, another race, are largely based on Arabic culture. For them, I went with Elder Scrolls Khajiit - their language has Persian and Hindi influences. It evokes the Middle Eastern feel without actually being (overtly) Middle Eastern. Of course, I couldn't use Khajiit names for the cities and nations, so I had to go with Middle Eastern names there, but again - I can pick and choose names that fit the overall theme I've created.
This leads into my final point: If you want to use something that's "close but not quite", there are dozens of pop culture generators that are based on real-world cultures - French, Spanish, Middle Eastern, Oriental, Russian, English, and about a dozen each of elves and dwarves. Go dig through them, and you can find all kinds of cool stuff.
Edit: I forgot something: naming conventions. 99% of the names you see in fantasy are either (first name last name) or (single name), because that's what you see in western culture. The real world isn't like that, though, and neither should fantasy worlds. Besides the "normal" names, you have:
* Surname-given name (common in Oriental cultures).
* Given Name-clan name
* Given Name-son/daughter of-(last name) - Scandinavian and Scots-Irish (-son/dottir, O', Mc, Mac, and nic')
* Given Name-surname-patronymic (Russian)
And of course, you can make all kinds of variations thereof. The Ma'jaat, for example, use <given name> <son/daughter of> <clan name>.
Honorifics (polite forms of address) are also something that can add color to a culture. Eastern cultures are big on honorifics - Japan has a ton of them - but they appear in almost every culture - Mr., Ms., and Mrs., Dr., Esquire... those are all honorifics. Instead of going with the same tired old "master" and "mistress", toss out a <last name>-sen or eare-<last name> (that's "honored" in Frisian, a term that could be used for someone of great age or learning, or simply respect. Google Translate is a great resource.)
* Fantasy Name Generators: 900 generators and counting (despite the title, it covers real-world and sci-fi names too).
Separate names with a comma.