How can you tell if a guy is going to ask you out?

If they are spending more time around you than they need to, that's usually a sign that they want to ask you out.

It's all in the eyes. If he looks you directly in the eyes and smiles, quickly looks away then back, or acts like a show-off, he digs you. If he's really nervous when you try to talk to him, that is a great sign that he's into you. If I have to condense body language down to a simple phrase, then my response is 'watch his eyes, if he looks into your eyes he's attracted to you. Good luck and hope this helps a bit, Kyle

Well he could be looking at you a lot or just talking to you every chance he gets or not talking at all.

If he's acting kinda strange.

Depends on the guy! a lot of the time the only way to tell is to look inside of you and determine whether you think he's sending you signals or not! (I've never said anything so cliché or cheesy in my life before XD)