1) AVOID MISTAKES: Mistakes like handing the wine glass wrongly, laughing unnecessarily,e.t.c...... 2) If you didn't storm the party with friends, immediately look for a group of friends to hang out with comfortably. Your ex must not see you in that "awkward lonely mood" especially when there are the ones who broke up with you. 3) DON'T PLAY ALONG: At the party, your ex will eventually want to make you jealous by flirting unnecessarily with others. Please "don't play along", just let them play their unhealthy games alone and end up the player playing without the other side. 4) IN CASE OF CONVERSATION : If a conversation is raised between you two, it's okay to talk to each other. No need being rude. Also, the conversation has to be limited thus it shouldn't go personal. During the conversation, don't act rude or needy and treat them like an acquaintance not an "ex". 5) Enjoy your party but don't get drunk and act stup...