What does it mean if he avoids eye contact?

Check it out. From a guys point of view, never get caught looking at the girl, if she's staring, avoid it and play it off like your not interested. In the case of sitting down and looking at each other, the only way to tell if he is interested is to keep your peripheral vision open and catch him looking at you from the corner of your eye. In the case of walking past each other, all he has to do is glance at you, and that means he's interested. If he wants to be friends, he will probably do none of these things. Don't tell anyone I've let you in on these secrets, I could be outcast.

If you have caught the guy looking at you several times, but doesn't give you eye contact when you look, its possible he likes you but is playing it cool. If he hasn't looked at you and isn't looking at you, it means he's probably not interested.

Having said all this, remember guys are more obvious than girls, we tend to look at girls more blatantly to make them aware we are interested. So id be careful about your hopes for this guy, instead look out for guys who like you, cos they will be looking at you to make it clear they like you :)