Guys!--How do you let girls know you like them?

I'm 14 and I really like this kid, and i think he might like me too, but i can't tell. I flirt with him all the time, but subtly, you know not to scare him or anything, and i think he;s flirting back, but i can't tell exactly. How do you guys flirt with girls so they know you like them and not "just being friendly"?