Characters to me are the single most important thing about a book. Of course your plot is relevant; you need to have a decent storyline, but unless your characters are leaping off the page, no one is going to want to read it.
The characters are going to be on the journey with you and they need to be interesting, if not always likeable, for you to want to spend three or four hundred pages in their company. This is why I put a lot of time into developing mine before committing them to paper.
It is not just a physical thing. Yes, of course you have to know how they look, but you also need to get to know their personalities. Are they confident or shy? Perhaps they are mean or selfish or have a kind heart. Where do they come from, do they have an accent, what was their family life like growing up? Then there’s things such as relationships, tastes in food, music or television, the way they dress, the little personality quirks that make them individual.
Build your characters on paper and in your head. Have conversations with them; get a mental image of how they look and the kind of thing they would say or do in certain situations. It is up to you to breathe life into them, otherwise they will come across as one dimensional and no one is going to want to read about them or care about their fate.
I can’t speak for other writers, but my characters are never based on specific people. Sure I may take a personality trait or two, but in my head they are entirely my creation. As the author though, I am sure each of them has a little bit of me in them.
For example, Angell is a cat lover with a fondness of pizza. Hmm… sound familiar? I could also be accused of sharing Hickok’s direct approach at times. I’m not very good at pussyfooting around an issue. I am a little more polite, but if I want an answer I will ask the question, and I definitely have his sarcastic streak. As for Vic, well he’s a bit clumsy, likes sitting on his ass and has a fondness for stuffing his face with junk food.
Nah, that doesn’t sound like me at all.