1. Don't talk about your ex
You have talked about how it ended at first with your friends but it is over now. Don't tell anything about your ex anymore.
2. Don't call
Whatever happens. You may madly miss but if you call your ex, you will go back to the beginning.
3. Don't reply
Sometimes it can be the other side who calls you to check how you are but don't reply.
4. Don't go
Don't go to the places that your ex hangs out or you used to go when you were together not to remember memories.
Ignore when you come across with your ex. Or just say "hi", nothing more.
6. Don't ask
Don't ask your friends about him. Especially to your mutual friends as they may tell your ex.
7. Don't be hopeful
Don't think about coming together again. Or else it will be almost impossible for you to forget.
8. Don't look
Don't look at the things that your ex gave you. If you can, just get rid of them.
9. Don't lock yourself in the house
10. Don't find a new person
Don't find a new person to make you forget about your ex. It will be bad for both of you.