Whatever your writing now, whether it is a short story, novel, play or anything else, what would happen if you actually met your main character? Would you get on? Would you love them, or hate them? Would you sit in a bar and catch up like old friends? Are you so similar you would argue? Or would you be so intrigued to meet them you would have to drill them with 20 questions?
Take half an hour and write about what would happen if you met your protagonist, it might just help you get to know your character better.