The classic move on making an ex jealous is letting him or her see that you've moved on with a new person. Knowing that they've lost you to someone new will make them jealous and perhaps a little angry. However, if they're the one who broke your heart, they deserve to be jealous and see you happy without them. There are several ways to go about making your ex jealous by getting them to think that you have a new boyfriend or girlfriend in your life.
The first opportunity you can create to make your ex jealous is to run into them. Since this person was your ex, you know what places they frequent and their usual schedule. Choose a place you know you'll run into them but won't be such an obvious place they'll know that you planned the encounter. The best kind of location to make them jealous will be a place you would have gone to anyway. Do you both use the same laundromat on the weekends or visit the same nightclub on a certain night? Run into them there and make your ex jealous.
Plan to look extra hot and sexy when you have this "chance" encounter with them. Ask a friend to find you someone who will pose as your new boyfriend or girlfriend as you run into your ex in an attempt to make them jealous. Be flirtatious with your date but don't overdo it. You ex will catch on that it is an attempt to make them jealous and you will not accomplish your goal. The best thing to do would be to act as you normally would with a boyfriend or girlfriend with your date. Later, when you run into them, act civilized but do not rub it in. This will give the illusion you have really moved on, which should make them jealous and want you back.
The second step you'll want to take in maintaining this illusion is starting a rumor that you are dating someone else. Let your friends know that you are attempting to make your ex jealous and ask them to start a gossip train indicating that you are dating someone gorgeous and treats you good. As soon as you ex hears the news, they will be filled with jealousy. This rumor can also work to your advantage in making them jealous if you spread the rumor before they run into you in a mutual location and see you with a new love.