How to tell the difference between a guy who's interested and a guy who's just friendly?

[walbreeze]

I am attracted to a guy in my class and am not sure if he is interested or just being friendly. I recently ran into him at a club and we never talk in class but he stopped to talk to me for a little and introduced himself to my friends.

I decided to add him as a friend on Facebook, even though we only have one mutual friend but he accepted anyways.

In class, he didn't look at me much only like a couple times then looked away really fast. When we passed around an attendance sheet to sign, he forgot to give it to his friend and gave it to me right away (I sit in front of him and his friend is next to him-catty corner behind me). He didn't notice until his friend told him he needed it before it was passed forward and he just laughed slightly embarrassed.

Then we were grouped together and he listened to my ideas and laughed at my "jokes" and would make frequent eye contact. He was very friendly and smiley. Also when he left class at the end, he looked back, I smiled at him, which might have been weird.

But I guess I'm not sure if he's just being friendly and himself or if he could be interested in me? How do you tell the difference?