1. Don’t blame her behavior on her period. Which should be a given. Not only does it invalidate how she feels but it’s counterproductive. “Is it because you’re on your period?” very rarely yields a calm response of, “Oh, yeah, that is it. Never mind!” It makes her frustrated, probably angry, and then everyone gets tense. Don’t do that. Instead,
2. Be patient. She might sound irrational for whatever reason and it may bug you, but relax. Unless she’s being physically or emotionally abusive (which probably has nothing to do with her period, frankly), try to understand where she might be coming from instead of brushing her off as “hormonal.”
3. Her favorite snacks/foods. At the end of the day, it’s still a hormonal situation. She’s going to have huge cravings for certain things because that’s the nature of her body chemistry. Bring them to her. Bonus points if you don’t even have to ask what she wants. This doesn’t make you a saint or a savior, it makes you a good boyfriend (or girlfriend).
4. Suggest a night out for whatever she’d like to do. If you’ve been avoiding that play she’s been excited about, now is a good time. If there’s a movie she won’t stop hinting at, go see it. Whatever it may be, just do it. You should be making such compromises around the clock but if you’re dragging your feet about it, again, now is a good time.
5. Suggest a night in for whatever she’d like to do. Because, hell, most of the time she might not want to do anything after coming home from work. So, bring her favorite dinner and settle down for games, movies, puzzles — basically whatever strikes her fancy.
6. Advil. Or Midol. Frankly, most women will probably have something like this already, but in case they don’t, it’s the quickest trip to your local pharmacy.
7. Be attentive. After speaking with a few friends on the subject, some women want a great deal of company and affection, while others just want to be left the hell alone. Still others want a balance between the two. It’s part of your job to pay attention to those needs and considerations. It’s easy to do and will make you both feel great and more connected.
BONUS: Invite her friends over to her place and make them all dinner. Sure, it’s some real Paul Rudd type shit but it works wonders. Doubt me all you want but I’m giving you gold by the ingot right now. You’re welcome.