A couple of posts ago, I quoted author Jack Gantos on getting ready to write. I thought you might also find his tips on characting characters interesting:
"Generally I just start writing without any goal in mind and allow the character to generate from the accumulated words that gather on the page.
Or I draw loosely and conjure up a character from the drawing.
Or, I pay close attention to people I find interesting as I walk down the city streets, or in libraries, or at the mall, or in grocery stores. I find restaurants are a very good place to find characters because people are very honestly themselves when they are hungry."