1) Don't contact him. Delete his phone numbers and block/unfriend him from your social media sites. This will prevent you from the need to call him or look at what he has posted and his photos. You should also store away his photos or tear them or burn them.
2) your heart is the one that is mostly heart because it's the one that fell in love with your ex. Always tell yourself the relationship is over; you've to move on.
3) When you think about your ex, snap out of it very fast. Tell yourself that you've to stop thinking about him. He is no longer in your life. You've to move on without him.
4) If you've anything that belongs to him, store it away/return to him or burn or destroy them. His things will always remind you of him as long as you've them.
5) Whenever you meet each other, whether at school or workplace, fight the need to ask for a reunion or to beg him to take you back. Greet him by trying hard to smile and then go your way. When you feel you want to talk him, fight the urge by reminding yourself you've to move on, you've stop behaving childishly, he's no longer in your life.
6) If you still hate your ex and you're bitter towards him, deal with those emotions. Stop hating and being angry at him. They will make it hard for you to heal and recover from the breakup and to move on. You won't be able to control yourself and you would wish to be around him.
7) If you feel like crying, cry as much as you can when alone. This is nature's way of dealing with hurt. After you've cried, tell yourself, "Relax. Now, smile and remember you're no longer with your ex. Don't behave as if you're with your ex. You've to heal and recover from the breakup. Do all you can to ensure you have healed and recovered from the breakup."