Characters play just as many roles in the writing process as they do in the novel itself. Some characters spark the very idea of the story, others show up when needed to suit plot, and others are doomed to life as nothing more than spear carriers. Most of the time, by the end of a first draft you’ll have too many, and some (if not all) will be flat as cardboard. Now’s the time to start bringing them to life.
Get Real, People
Characters will pop in and out as you write, even if you aren't sure what to do with them or how they fit. Some of these characters will be stars, others will be people for your readers to trip over as they navigate the story. After you've figured out
which to keep and which to cut, you'll likely want to develop them more and make them as rich and three dimensional as your main character. Or, you might be the type who prefers to flesh out everyone after the fact once you see how the story unfolds.
Try looking at what role each character plays in the story. Not their "the protag's best friend" type role, but a
thematic role. For example, in
The Shifter, Aylin is the voice of reason. She's the practical one when Nya gears up to dive headfirst and full speed into something she believes in (she a bit of an idealist). Knowing this, as I edit I keep Aylin's role in mind. Her style and behavior should reflect her personality and role, both as the best friend,
and as the voice of reason. Her actions will also reinforce this.