You don't. You just have to try and think about their personality types and whether or not you can imagine them fitting together.
its best to ask her out, before someone else does.
He likes his other friend.
if ur friend likes him, then let ur friend have him, chances are that will hurt ur friend if she likes him, and i wouldn't risk a friendship over a guy.
If he acts different around you then the way he did before
If you don't know if your girlfriend likes you then you need to get to know each other better because she should like you before you become girlfriend and boyfriend.....
ask him
you will know that he likes your friend because he will always bring her up and he will want to be around her.
If a guy likes you as more than a friend, he will likely ask you out on a date. Before that, he might ask your friends for information about you to try to find out if you already have a boyfriend.
Unfortunately if he likes someone else and is a friend of yours let her know and be happy for her - there are many other guys out there to pick from. the other thing is to find out if she even likes him. If not try to move in
If he or she is a little more closer and wants more hugs, kiss on the cheek etc., he or she might act unusual than before as a friend.
Well just TALK to her find out if she likes you back but before that make sure you know it wont ruin your friend relationship
you ask his friend if he can ask him!