What do I do when I like a guy, and he likes me back, but he also likes my best friend? My best friend doesn't like him though. So how do I win him over?

How old are you, your friend, and the guy? Why are your ages important you ask? Because that lets me know how many details to give you about competing with a friend for a boys attention, when he likes you both.

Its his choice really, but even if you do win him over, he still likes you both, even if your friend has no interest in him, he will still have that interest to deal with, and its better to let him make the choice on his own, without your influence.

Basically, you treat him the same as you have been, and let him make up his own mind, for himself.

That's why ages are important.

If he likes your friend too, forget about him. He can't possible be so into you if he also likes someone else. You'll be just stuck competing with your best friend and keeping that friendship is more important than this guy.