For guys only -- how do I no if this guy in my class likes me?

if he gets silent for a a few seconds and takes extended looks at you in the middle of a conversation. if ur still not sure try turning the flirting up a notch and he'll get the hint

the way he looks at you with a slight sparkle in his eyes and a grin in his lips usually gives it away. maybe ask some of his guy friends he talks to, usually your girl friends who see you two together a lot can tell as well. try dropping a hint or two to see if he moves in on it