Beware of Stereotypes
We all know the stereotypes of both literature and film. The damsel who never contributes anything but needs constant saving. The evil dude wearing black. The ditsy blond. The idiot sidekick who is absolutely hilarious in his stupidity. These and many others are the stereotypes of storytelling.
Stereotypes have their place, but it's not in most literature. The exception is humor. If you're writing comedy, you might want to make use of exaggerated stereotypes. It can be funny to read about the ditsy blond or the sidekick who can't get anything right. If your hope is to induce laughter, literary stereotypes might be the way to do it.
If you're writing anything other than comedy, avoid stereotypes at all costs. There are a few instances where you might be able to make use of the black hat stereotype, but most of the others are out. Stereotypes are like cliches. Used right and sparingly, they can enhance your story. Overuse them and you're certain to turn off even the most determined of readers.
If you want to use a stereotype, try changing things up a bit. Perhaps your good guy wears black and walks around with a scowl on his face. Or maybe you have a guy who needs to be rescued by the beautiful damsel. By playing with the stereotypes you'll create greater depth in your characters and enhance your story.
Bring Out the Flaws in Your Characters
Everyone has flaws. You, me, the mailman, all of us. So one of the rules of creating fictional characters is that no one can be perfect. The exact flaws are many and varied, but every characters must have at least one flaw. Maybe the character in question has a fiery temper, maybe he never looks before he leaps, or maybe he's afraid of commitment. Whatever. But he needs flaws.
Once you have these flaws worked out, show them to the reader. Let your readers see these flaws, and consider exaggerating them when necessary. Not to the point of silliness (unless you're writing comedy), but enough that your readers don't for a minute think the character is perfect. Avoid the stereotypical traits (redhead with fiery tempers as their only flaw are really quite annoying), but flaws are what will make your characters come to life.
It's All in the Name
Naming your characters is an important thing, but there aren't a lot of rules regarding the names you choose. You can name your characters anything you'd like, but there are some conventions you might want to stay away from. Don't use anything obvious, such as naming the guy who's going to betray everyone Judas. Don't use the name Jezebel for a woman who is a false prophet or for someone who will eventually become a prostitute. Too obvious.
Play with names until you find something that fits. And don't let anyone tell you that you shouldn't use a name because it might offend someone. If you do that, you'll never be able to name any of your characters. Someone somewhere in the world will have that name, and that someone may possibly be offended. Choose a name based on your character, and don't worry about what people might think.
If you're worried that a close friend or family member may be offended by the use of their name, change the spelling. Vicki can become Vicky, David can become Daivid, Jamison can become Jamyson. This works especially well for speculative fiction (such as fantasy or science fiction), but odd names work in just about any genre.
Think carefully about your fictional characters and consider everything from names to personality traits. Your job as an author is to bring your characters to life. To do this, follow the most basic of rules and fill your characters with believability.
