First you have to know that you really love him, and if you do then make him think your not interested, and you get a fake boyfriend that will make him super jealous. This answer is not garenteed, but it works with my cousin. If that doesn't work wear his favorite outfit that makes him stop and stare.
You don't.. you wait for him to regret how foolish he was, and come back to you. If not, then it wasn't meant to be.
get a new girlfriend or boyfriend
show her that you loves her more than her new boy friend and point out all of the bad things about her new boyfriend
You don't ! Your relationship with him failed for whatever reason. He has a new partner - you have no right to interfere in their relationship in the hope of winning him back !
Choose between them, if you left your ex for a good reason then continue dating your new girlfriend/boyfriend.
If she is happy, leave her alone. She has already replaced you and it hurts, but she has moved on. You should too. Be her friend, the opportunity may arise in the near future. If you try to get her back now, you risk alienating her and hurting her relationship with her new boyfriend. She may end up hating you for that.
Simple Answer: You don't.
Does she have another boyfriend? If she does you can embarrass her in front of him. also you could get a new girlfriend if you don't already have one and show your ex whats shes missing. but shes single and jealousy is just rude
Unfortunately she has moved on and so should you.
You do absolutely nothing about your ex boyfriend considering he has a new girlfriend. If he loved you he would break up with his girlfriend and since he has not then he wants to be with her and you need to accept that. Just because you have broken up with your boyfriend it doesn't mean you can just step back into your ex boyfriend's life.
Let him have a threesome with your sister (only if hot)
Dump him. He is a playa