If you know the guy, I would say trust your sense of intuition. Some guys will hint at it for a while before making a move (ie, describing a girl that they like but don't want to ask out for fear of 'complicating things' who perfectly matches your description).
Ask him.
You have to get to know him first, before you ask him out.
The best way to know is to ask him.
You will never know if you don't ask.
Ask him
ASK
how you know when a boy has a crush on you is when a boy looks at you all the time. or text him and ask or call just be yourself about it when you ask
You cannot know for certainYou cannot know unless you were to ask them. Even then they could be lying. Ask the boy and the girl that you believe the boy is going out with. If they both respond yes. Then chances are good that they are going out.
Have a common friend ask.
ask him what he likes
Ask him.
Dont do that!!! You Dont know the guy that's why he is the new boy!! Get to know him talk to him!!! Then if you see that he is a great guy go for it ask him!!! I wish you well!!