Why are teen boy's scared to let a girl know they like them? And how can I tell if he does without word's.

Just look for signs.
If he likes to spend time alone with u
if he stares at u with a weird smile on his face
if he acts stupid around you
oh also if hes soo far into denial that hes really mean to you so that nobody suspects a thing.
Guys wheel girls in different ways.. :P

They don't, most just care about what others think.

Look at his actions and movements u are bound 2 no.

They're worried that you'll turn them down, afraid of being made a fool of. Also, brittany's right, they do care about other's input. Sad but true.