Perhaps you have no idea about her likes and dislikes. If so, you're not really looking at her or listening to her and picking up upon the messages that will be clearly conveyed through several different mediums. What does her style of dress tell you? What do her hobbies tell you about her? What do her friendships and habits say about her? What does the way in which she speaks or moves or behaves tell you?

Once you start looking, really looking, you will realize that you can work out quite a bit about someone even from across a room. All of that previously subconscious information provides you with clues as to what might be the best way in which to chat her up.

All you need is the confidence to be able to step into her shoes and trust in your instincts. And whenever doubtful of your best approach the use of humor is a good back up plan, although once again you do have to fist ask yourself the question "what will SHE think is funny?"