Depends on what you did, and whether he is willing to forgive you.
A sincere apology would be a good start...
Good luck
make him jealous
You don't.
Win the lottery, or have a miraculous experience. Please do not hold your breath .
ignore him and let be seen with a cuter guy.
dont just dump him
You can't trust her anymore. Give up.
Give him a reason and tell him why you did that..
Stay out of it! You had your chance with her and it didn't work, so as long as her boyfriend is still around it's best to move on. If you find you still love her in a few months then the only time you should feel free to try and win her back is when and if she break-ups with her boyfriend. Yes if you have feelings for her you need to at least try to get her back.
How to Win Your Ex Boyfriend Back? I recommend this ebook http://bit.ly/9nUo78 thank you.
Be sexy, try to be hard to get but constantly around him at the same time
Thats impossible
talk to him all flirty and make him want you