While I'm writing my daily pages (I'm starting at the beginning of the book, but might hop around later), I'm also working at the same time on fleshing out my characters. Since I'm writing mysteries, I'm thinking in terms of suspects, killer, and victim(s).
A lot of these characters have traits of people I know or have met, even for a few minutes, in the grocery store or Target. Sometimes I meet people that really strike me the wrong way and they become victims in my books. :) The idea here is that you're writing what you know. Obviously you're not going to want to call your characters by the same name or make them exactly like the person you have in mind. That's called libel. But there's lots of good baby naming links for names. Or you could drag out your old high school yearbook and come across a bunch of name ideas. I've had fun with this site: http://www.seventhsanctum.com/index-name.php . It has a lot of fantasy name ideas, but it can really get your creative juices flowing.
It's been said a lot, but it really helps to know your characters well. It helps even more to know your characters a little TOO well. If you make a simple list of your character's personality traits and background, it helps you to know what motivates them and what internal conflicts they might be facing. You don't need to put all your information about the characters in your book--it would end up bloated with unnecessary information. But by knowing your character well, you can make your book stronger.
Here are some links to some character trait charts that have helped me nail down my characters: http://users.wirefire.com/tritt/tip8.html and http://www.charlottedillon.com/CharacterChart.html