ANSWER
Sometimes, not all the time, guys avoid you when they know you like them. Why? Well, it's probably because they don't like you back, and don't wish to be seen with you so they avoid you.
Maybe guys seem to avoid you after they find out that you like them because they are intimidated by your beauty. Talk to them and make them feel comfortable about being around you. Hope that helps.
because they dont like u back
It depends on the shyness of the guy. Some guys are cocky, others aren't and usually it has noting to do with whether they like you or not, when they avoid eye contact, you know they have noticed you so usually that means they like you.
stalk them
Most likely, they don't want to take responsibility for what they did.
Sometimes, yes....they are afraid they will do or say something that will embarrass them or make them look stupid in your eyes. Other times they are avoiding you because they really don't like you and don't know how to say it.
Weird. You can see them looking at you, joke around you, or even avoid you. something like that.
Tell them!
I don't think that's really true, but if it is, Guys look for girls like them, so if you're skinny and he's fat, You might not be the best couple...
Well I am a guy and I don't like it , I see it as an act that diminishes my manly properties , and I can assure you most guys have the same thought of not liking it. 'Most guys' - how many do you know? Most Guys as in 90% of the people I know in my society , and you can know the whole society's guys opinion , since in our eastern culture it never happens , and all of the people I do know , dont like it . Some chaps that I know think it's sweet.
Well the guys I know laugh.
Definitely man-up and let her know. Most girls are more timid about letting guys know they like them than guys are. Go for it!