How do i ask the guy i like out?

so there is this guy at school that i like but i don't really ever talk to him. we are now on summer holidays so i cant talk to him at school what should i do? he is a really nice guy and has always been nice to mee.g like inviting me to sit with him and his friends when he thought i was sitting alone at lunch. he hasnt shown any interest otherwise though. i dont think we are in any of the same classes which is a problem but i see him in the library all the time. so how should i ask him to hang out over facebook ? (im 16) and he is 17 i think :) thanx