I write “by the seat of my pants.” If I outline, which I dislike doing in the first place, I lose interest in writing the story–it’s like reading a book for the second time immediately after you just read it for the first time.
But I’ve found out after writing several novels, that there are some tricks that can help me with both character AND plot.
So, what I do now is think of several characters and start writing. After one or two chapters, I probably know what they do for a living, what they look like and some tiny bit about their personalities.
But I need more. I need to know their secrets. The sooner I know their secrets, the more I can ratchet up the conflict and tension for them. Because of course, they don’t want anyone else to know their secrets, so they’ll often do things than are unreasonable to keep them.
Each character also needs to be motivated by something. And then I have the fun of putting obstacles in her way to creative tension and conflict here, too.
So, two important ways to help yourself have interesting characters your readers will care about is to give each one (even many of the minor characters) a secret or two, and something they want badly. If could be that what they want badly is to hide their secret.
It’s up to you when to divulge the secrets. Often it’s best to wait awhile to do that, but other times it’s good for the reader to know almost right away because it explains why the character acts as she does. And it’s always delicious, isn’t it, to be in on other people’s secrets?