It's just that we like regular attention. Consistently. All the time. You would think that the fact that you took us out to a fancy dinner last night should earn you brownie points for at least a week. But it doesn't. It only gets you about 24 hours. If there isn't at least a phone call within 24 hours, your stock plummets. But see how easy is the solution? Just one measly phone call. It's all we ask. And for some reason, you have to call pretty quickly after having a good time together. You have to call right afterwards, the next day. And then you can take a couple of days off.
The attention thing is what leads--in the extreme--to girls getting cranky in front of your friends or family. I even knew why I got cranky in front of my ex-boyfriend's family and I still couldn't stop it. It's hardwired somehow. But there's an easy solution. You just need to make sure you give her a bunch of brief respites alone. Drag her off to another room for a few minutes every once in awhile. Even every hour if necessary. At the very least make sure to tell her that you're psyched you're going to get to be alone with her later.

Also, we like to be complimented. Fun, spontaneous compliments. "Wow, you look good," when you first see her. It's not so hard. Just do it.

In fact, just talking about the woman is a good thing. If she's talking about a problem at work you respond with "Well, you could handle it the way you handled this, or that." It means you've been paying attention, figuring her out. A definite plus. Or talk about her to the group, too: "Jenny has a funny story about that." It's great when you're standing next to a boy and he says something about you to a group that announces to the world that you have a connection and that he knows something about you. God, I love that.

Anyway, you get the idea. I will not for one second defend these female needs as rational--but that doesn't mean you're going to be able to reason her out of them. They're there and they're not going to go away. And if you don't keep up your end of the maintenance bargain she'll throw total fits and become even more high maintenance. So do it and don't complain.