I have just read trough a long blog by a guy who works at a publisher. His job is to accept or reject the manuscripts that the publisher receives. The guy has been kind enough to show the most common mistakes he has seen, and why he rejects so many of the manuscripts. The blog is old and no longer active.
Since the blog is in that funny Norwegian language, I'll translate and shorten what I learned from it. You have probably heard some of these before, but I guess a little repetition won't harm. Some of these are pretty basic.
This is probably self-explanatory, but I leave it as a reminder. A story needs a protagonist (the guy whose actions make up the story), a goal (what the protagonist wants to achieve) and an antagonist (the guy who wants to prevent the protagonist from reaching his goals). Remember, the antagonist does not have to be another character, it could be the protagonists own low self-esteem, or like in Robinson Crusoe, the world itself. The suspense of the story also has to increase, make it difficult for the protagonist to reach his goal by increasing the strength and influence of the antagonist.
IT HAS TO MAKE SENSE
Your protagonists actions has to make sense. Never let he or she do something without a reason, i.e. hide behind a couch when he is not in danger. Many do this without noticing it, because it makes sense for the writer and it helps the story onward. Since the protagonist hid behind the couch, he was able to overhear something that drives the story onward. Him hiding behind the couch in the first place still does not make sense.
DON'T SHOW AND TELL
Stick to one. Never say something like.
"You are an idiot, and you smell like shit!" Joe insulted Vivian. Leave the insulted, we understand from the sentence that Joe is insulting Vivian. Another example: One of your characters is angry, saying and doing a lot of stuff that shows that he is angry. Never write "Joe was angry" when you have already shown that he is angry by describing his actions. The reader understands that without you needing to tell them.
SOME THINGS ARE BEST LEFT UNDONE
Are you writing about vampires? Or maybe a school where children are taught in the ways of magic? Don't. Do not try to ride the popularity wave. When Twilight was at its peak, 1/3 of the manuscripts was about vampires, and needless to say none of them ever saw the light of day. It's hard to stand out when everyone is writing about it. Be original.
Never let your protagonist be perfect, it takes out a lot of the suspense. He should have some flaws, or disadvantages, which makes the plot more exciting. A perfect protagonist leaves the reader feeling that the protagonist is hollow and of no importance - but if he has some flaws the reader will easier relate to him because he is more realistic. In real life, we all have some sort of flaws. Your characters should too.
Does one of your characters originate from another country, or speaks another language as well as English or whatever the language you are writing in? Then don't overdo the por favor's and the no grazie's if he is from Spain, or the M'bwana if he is from Africa. A few here and there is OK, but people tend to overdo it.
WHO ARE ALL OF THESE PEOPLE?
Try to keep the number of characters low, and don't introduce heaps of people at the first chapters. Do not start off a novel by describing a family with all their names, what they do and so on. Stick to one or two, and introduce others along the way. Give the reader the opportunity to learn who is who, and make it clear to them who is important and who is not. Feel free to introduce people as "the bartender", "the taxi driver" and so on if they are of low importance. Don't feel like you have to give everyone names. The reader hates to have to go back and forth trying to remember who is who.
GET DOWN! JAMES YELLED
It seems as if everyone is afraid of sticking to the basic way of displaying dialogue. "Get down!" yelled James. "Get over here" whispered Joe. "I do" Vivian answered. What is wrong with "Hello" said James? According to the blogger, almost every writer is trying to mix these up as much as possible because they are afraid of being repetitive. They are using all sorts of other words instead of said. The thing is, we (the readers) are used to reading ... said James after sentences. Because of this, reading ... said James is almost a subconscious effort, while reading ... yelled James is not, and therefore takes some of the attention away from what is told in the dialogue. Keep it simple and focus on the dialogue, said James.
Love 'em or hate 'em. Tolkien wrote prologues, therefore every aspiring fantasy-writers are doing it as well. If you really feel you have to, then do it. But the reader has to get hooked from the get go, so heading straight into the action is a much safer way to go. Let all the wonderful descriptions about the world and the races be told by the characters thoughts and dialogues.Let them learn that the capital is named Axxoh'ruzzara, that the world is in chaos, that the King is a cyclops named Jieredan, and that there are galaxies, far, far away. If you have a prologue, know that there is a good chance that the publisher will skip it and head straight for the action to see if it is any good. Therefore you should really focus on the first part of you story.
This is pretty obvious, but the blogger sees examples of this all the time. Don't ever let some parts of your work seem unfinished, just because "the novel is going to be spell-checked, proofread and fixed either way before being published". Try to make product you send in as near the finished state as possible.
HOW TO DIVIDE CHAPTERS
This is important. If your book is divided into chapters (most of them are), you should do this in a clever way. Many separates the chapters according to the events that takes place. Chapter 25 - The protagonist barely escapes being captured. Chapter 26 - The protagonist is hiding from the bad guys. Chapter 27 - The protagonist gets captured again (yes, he is quite useless). This is not the way to do this. Let the events go along onto the new chapter. Don't end the chapter with something being resolved, this will make the reader put the book down at the end of a chapter. Let the suspense carry on over to the other chapter - and you got yourself a page turner. JK Rowling does this almost without exceptions, and needless to say it worked.
DEUS EX MACHIMA
This is common known, so I will keep it short. Never resolve something by playing God, just because you have written yourself into a corner. An example: James is about to be captured, but then he remembers he has a lockpick in his pocket, and is able to pick the lock and escape just before the bad guys get to him. Where did the lockpick come from? If you have written yourself into a corner, go back and fix it. Let James pocketpick the lockpick from a pocketpickers pocket a little earlier in the chapter.
A THEN B THEN C THEN D
This is bad. Never let your novel be a series of events that is happening regardless of each other. Mix it up. Event A happens, which causes B and C to happen. Then let the story derive from B, and save the C for later. An example:
Don't do this: The king died, then the queen died, and then the prince became king.
Do this: The king died, causing the queen to die of sorrow, leaving the prince to take his rightful place upon the throne.
(Sorry for the poor example, but I hope you understand the meaning of this)
HOW TO BE REJECTED
The most common reason of rejection is poor spelling and language. The blogger says that 50 to 60 % of the contributions are rejected after reading a few pages because of bad grammar. If you have problems with spelling, practice! Practice, practice, practice! Your ideas may be fantastic, but if your representation is flawed, you are going to have yourself a hard time.