Never bad-mouth the ex—and your husband (or partner) shouldn't either, even if the fur is still flying. Studies show that it's the ongoing conflict after divorce that hurts kids the most.
Corollary: "How could you have married such an idiot?"
Don't stand next to him when he's on the phone with his ex, making faces and sticking your finger down your throat. Don't write her letters or e-mails, and if she's a crank caller, get caller ID. Fighting about the ex—call it the 'ex hex'—is the equivalent of having a stink bomb thrown into your marriage.