Is there anything..?

I'm biual and don't feel comfortable telling straight people due to prejudice. I'm attracted to some of my friends (girls) but I can never tell a girl's uality. I just automatically persume that every girl is straight. Is there anything i can say/wear/do that only LGBT people will pick up on, so i can subtly "tell" them I am too? It's hard with girls because gay, or straight, we are all touchy and flirty with our friends.