I also get hit on by girls a lot more than I do by boys.
I try to be innocently charming and respectfully charismatic in return when it happens, especially when I know I probably won't be seeing them again. They've made me feel better about myself for a minute, so what harm will come of trying to make them feel better about themselves too? Who doesn't like to feel desirable or like a great catch? Flirting's fun. I just wish I had more opportunities to do it with people I was actually attracted to.