It definitely helps if you know what you are apologizing for. Most women don't like for you to apologize if you don't even know why. Just be straight with her and say that you are sorry for (insert problem here). Depending on how bad the problem was, you may need to give her some time to cool off about the issue before you apologize. Tell her you've been thinking about what she said and that you realized she was right and you are sorry for whatever it was that did (but make sure you point out what that was!) If you were completely right and she was completely wrong, you don't have to apologize to her for that. But it is nice if you apologize for the problem escalating so much if it did.