I tend to get lost in histories and such things, and I'm writing a story about one dude and his experiences. How much character building do I need to do for characters that the main character is in contact with. Do I include extra background for the sake of knowing the character? Example: Main Character-Thomas. Thomas is going home after a bad day. He runs into his landlord, who reminds him rent is due. Thomas may speak to this fellow twice more. He doesn't really know him, outside of the "landlord" role. Does the reader need to be informed that the landlord is an avid sports fan, likes the color green and thinks Posh Spice is the hottest woman in history? I didn't write any of that in, but I have gotten VERY mixed reviews of the story so far. (around 3000 words so far) Some want action action action. Some like description of scenes and thoughts and such. I need to introduce a mentor and a love interest, as well, but I don't want to "follow" those characters either. They will be more permanent characters, but just how much does the reader need to know? Should the knowledge be conveyed through Thomas' experiences with them or through narrative?
If the LL is a one and done kind of character interaction, then, no, we don't need his whole life story and hobbies and when he last went to the bathroom. I just responded to something similar in a different post about character development. Get to know your characters by writing some scenes with them. The scenes don't necessarily need to show up in your final story, but they'll let you get to know your MC and who the other characters that are important to him are. Action doesn't always mean some kind of heart pounding suspense or physical chase. It can be an internal dilemma - what he's thinking, how he sees the LL and wants to avoid him -- he wants to turn around and go the other way -- why is the LL here now? The rent isn't considered late for 2 more days. He's pretty sure he's going to be able to get the last $100 by then. Can he turn around? Damn -- he can't. He just caught the LL in a glance. Go to some dialogue. You could add a bit of detail, just to make him real or to give the reader a picture of him. EX: LL was wearing that dirty Green Bay Packers jersey. He probably did it just to stick it to Mo. Was that a drip of cheese sauce at the top of the number "3?" The game was two days ago. Sure, they beat the Bears good. But was it that important to throw the win in Mo's face that LL couldn't even wait until the jersey had been washed? What a dick. If LL was really that big of a Packers fan, you'd think that he'd get a new freaking jersey, since not only was this one dirty but it was ripped at the shoulder. "Hey, Mo -- I was just looking for you. Thought I'd get the rent from you since I was upstairs." Yeah, right. If the Bears had won, Mo would have the rent already. LL probably knew that. That's why he was here. Or whatever. This type of thing develops your MC as much or more as it develops the LL -- who knows if the LL really is like that or what his motivations are. But the fact that the Mo thinks this tells us something about him. If he thinks the worst of everyone, that tells us a lot about him. Your mentor and especially your love interest will need to be more developed -- especially insofar as how Thomas sees them. You want to develop as much as you can through Thomas' experiences with them, rather than with narrative. But you need some narrative to move the story along.
It varies based on the role the character plays in the story. Like movies, novels almost always have some "walk on" parts, and those characters do not need to be terribly deeply drawn. I would try to give them distinct personalities and have some basic sense of their back stories and motivations, though, as it will tend to make their actions and dialogue more engaging. I would also try not to overpopulate the world with walk-ons, and I would recommend keeping them in mind as you write. I have had more than a few "walk ons" spring to life and become full characters. So give them enough life to make them interesting, and they may just surprise you later and come to your rescue when you need them.
You the writer needs to know. And when you know, it will naturally be conveyed in the story as and when it comes up and you won't even need to make any conscious effort for that to happen. Having all that background knowledge makes the way you write the character and his reactions more complex and realistic - it doesn't really mean that the reader will ever find out what your MC's favourite colour is or that the landlord thinks Victoria Beckham is the hottest woman on the planet. The most important thing is to make your characters relatable.
A character need not develop at all. The term "flat character" need not be a criticism. In most cases, you do want the character to evolve due to experiencing the events of the story. But a character can also be a catalyst for change in the people he or she interacts with, and yet remain untouched. For example, Mary Poppins floats into a family's life, creates various disruptions that bring the family together and change their outlook, then packs her bag and rides away on the next breeze.
I write mostly first-person because I prefer NOT to let the reader really know what people outside the viewpoint character are like. The omniscient narrator spoils the fun for me. In first-person you see the world through a character's eyes. That leaves more room for the reader to interpret events/characters (Are they really like that, or is the MC just a jaded ass?), which is the way I prefer it. For walk-ons/placeholders, no you don't need there life story. For recurring characters/antagonists, yeah you need a general idea of how the viewpoint characters sees them. We all form preconceptions about people we know.
There is a difference between "walk on" characters, main characters, your central character (or protagonist) and supporting characters. You only need to inform the reader of what they need to know about a character if that attribute effects something in the story. Also, if it doesn't add something meaningful to the story, it's worthless to include it. Why does the reader care about the landlord being an avid sports fan or that he likes green or even women? Answer that rhetorical question. Now, does that answer involve something that the reader is actually going to witness taking place in the text you are going to write? If not, then the reader doesn't need to know. If so, then you had better mention it. But, take care - Walk-on characters can take over a story. That's not always a bad thing. What if the walk-on character is better than the main character? In essence, if you find yourself writing too much about a walk-on or supporting character, chances are you should be writing a story about them instead of your main character.