1. He was broke--Everyone has a different lifestyle and just because he couldn't match yours, that doesn't mean he's a bad guy-or even cheap. Don't sound high maintenance by complaining about his lack of funds.
2. Everything he thought/did/said was terrible--Even though you broke up, you shouldn't shoot down every good thing he did or every good time you had. If someone brings up a great memory of the two of you, take a deep breath and avoid the urge to say, "Yeah, but what about the time he did [insert something horrible here]." And definitely don't badmouth your ex in front of your new man. If your current BF thinks you may still have strong-even strongly negative-feelings for your past guy, he may wonder if you've actually moved on.
3. He was always a jerk--Well, then why did you date him for X number of months or even years? Saying this just makes you look bad, and worse, bitter. Sure, it's always important to look back and see if there were any red flags you missed-so you can be well aware of what to look for next time-but you don't need to broadcast all the warning signs to everyone you know.
4. You still love him--We all go through heartache and have experienced a breakup. Telling anyone that you still love him will only prolong the healing. Fake it till you make it. Reframe this to something like, "We had a good run, and I wish him the best." Even if you don't.
5. Anything super embarrassing about your ex--If you're willing to share awful story after awful story about your ex, what does this say to your pals or your current man?
6. Anything he told you in absolute confidence--Also, don't show you're untrustworthy by spilling major secrets about your ex's family, childhood, what have you. However bitterly things ended, the fact is that you were in an intimate relationship with this person. He's an "ex" so you may rationalize that any oaths made are off the table but keeping promises and living with integrity is just a good way to lead your life.
7. Qualities that you loved about your ex--Some people have the opposite problem when it comes to exes and find themselves gushing about the awesome things he did, gifts he gave you, how he made you feel special, blah blah blah. For the sake of any new relationship you might be forming, get your mind-and mouth-out of the past.
8. How much your parents loved him--When you take a new guy to meet your folks, don't compare how your exes did with your family-especially if your mom and dad loved someone you dated before. The guy is probably nervous enough trying to live up to your expectations-he doesn't need the ghost of your ex-bf taunting him, too.
9. The sex was bad--Unless your man just lay there like a dead fish every time you got busy, how good he was in bed is completely subjective.
10. Negative qualities your ex had that your current guy has--If you really want to piss your current boyfriend off, mention you hate something he does and that it totally reminds you of your ex. This kind of comment never leads to anything positive.