“I don’t have a very clear idea of who the characters are until they start talking.”
I find this to be true of my own characters. In a current novel I am working on, I was struggling to come up with a main character. I wrote numerous descriptions playing on looks, age, style and so forth. I could never lock it down though. Finally I got frustrated and just decided I am going to write and fill in the blanks later. This turned out to be a good thing. Once the dialogue began the character began to develop rapidly. It is times such as these where the same words come back to haunt me that I heard when I first started writing, “just write”.
There are times when we all over think a certain character, or plot in our writing. The only way to really move forward is to keep writing. Trust that your own abilities will eventually bring the story out. And as I said, you can always fill in the blanks later. But for now…just write.