If the boy has a girlfriend, find a guy that doesn't have a girlfriend.
being an introverted guy myself, here is my advice; I say let him know, and make it obvious that you like him and want to be more than friends!
the uninvited
ask him, or ask his friends
Find out what you are doing wrong.
You don't. That is not nice and if you know her is really mean. Leave him alone and go find someone who doesn't have a girlfriend.
Do some research, find out if he has a girlfriend.
They are very rare I'm one for example
If you dont know who the guy is then you should find out before being jealous. But if you do know the guy then you should just go have a long talk with your girlfriend because if you are jealous, your girlfriend might just break up with you.
Let them find out for themselves. If you intervene, you will be the bad guy.
He will put his arm around your shoulder and get real close.
If a guy tells his friends that his girlfriend is quality, he means that she is a great girlfriend.