tell them your not interest in anything beyond friendship and then use that friendship with them to say positive things about your friend who has a crush on them in order to turn their attention towards your friend.
Do not give up. If your friend knows that you like him/her then she/he will turn the person down. But you need to tell your crush that you like her/him. That would make things easier on you.
I think you should go and tell your crush about your feelings because unless he does not come 2 know that you are in love with him how will he turn towards you. Keep showing your crush how much you are in love with him and 1 day he may towards you.
If your crush asked you out and you are only 12 years old, simply turn his request down.
Unfortunately theres not much you can do. If he is gay its very unlikely that he will turn straight. Although it might be hard to accept its best to enjoy his company as a friend.
get him into bed.
I was in the same spot as you. When you like your friends boyfriend its difficult, DO NOT flirt with him, because he could go and turn to your friend, if it is just a crush try to ditance yourself, and ust be there for your friend. but if you think you really like him i would talk to your friend about it. BUt dont say somthing like "i have a huge crush on your boyfriend". think before you speak and what you think is best.
you back off and tell your friend that she already had her chance to date him and that it is your turn you back off and tell your friend that she already had her chance to date him and that it is your turn
You could try talking to her about how you still want to be friends.AND hey sometimes things turn out in the end (I have a crush on my best friend)
if you believe that someone is using your best friend then you should try to inform your friend of your thoughts. try to be calm when you are telling your best friend as you don't want the conversation to turn into an argument. if you have any memory of that person using your friend then mention the experiences to your friend in the conversation but remenber to be calm and keep your tone down.
dont turn your back on him
It's not a good idea to steal your best friend's crush. If she/he is your best friend you wouldn't let anyone come between that. Crushes/bf's/gf's/ ruin friendships. So second guess that idea. I've done it before, and it did not turn out well. Both of us liked the same girl, and i was trying to win her over. Now because i did that every1 makes fun of me becuz i like her, so expect if you do that the same will happen to you.