Livia Blackburne's post On Writing Realistic Male Characters is a bit of a help there. So is seeing stark yet subtle examples of the differences in the way men and women view the world.
For instance, I've just finished Doctor Who Series Four (for the second time), and something about the end of it was bugging me. What I'm about to discuss has spoilers, so for those of you who haven't yet seen the show, but plan to, and want their viewing experience to be spoiler-free, I'm putting the rest below the fold.
Right. All present and accounted for, aside from the non-spoiler sorts? Good. Great. Let me set the scene: in Series Two, The Doctor's companion, Rose Tyler, ended up trapped in a parallel universe. Considering how close the two of them were, it was terrible for both. She loved him, he loved her, and twas sad stuff all round.
I mean, just look at the two of them and tell me they weren't something special:
Drove. Me. Nuts.
One, she's already been through one of The Doctor's regenerations, and that had turned out great, so why would she worry about it? Two, he was dying, she loves him, and she should've really been screaming at him to get on with the whole regeneration thing before it's too late, not sitting there wanking about him changing. Three - oh, fuck it, I'm tired of pummeling Russell T. Davies.
So that weighed on me. Worried at my mind for a few days. It was like having a tiny little rock in my sock, driving me absolutely mad. And then I had it, the reason he hadn't got it: he's being a stereotypical boy. Physical appearance means a lot to a guy. Whereas a woman, meh. Yeah, ladies like the good looks. But we aren't quite as fixated on them. If the person we've fallen for is still going to be pretty much the same in mind and emotion, we can get over the physical package. But apparently, that never occurred to Russell T. Davies. So he had Rose being a wanker. Argh.
Contrast that with a story arc from Series 3, "Daleks in Manhattan" and "Evolution of the Daleks." These were written by Helen Raynor. And they didn't lack for kick-arse action - the lady, ladies and gentlemen, is fucking brutal. But she's also a she. And so we have a bit of a mirror element in here, with two of the supporting characters, Laszlo and Tallulah. In the beginning, we see that they're sweethearts. Then the Daleks snatch him away and turn him into a pig-slave (long story). His mind remained intact, but he wouldn't win any beauty contests now. He hid himself away from Tallulah, convinced she could never love a monster. But when she found out, though she was a bit squigged at his appearance, she loved him still, and they go on to what we can expect was a long and happy life together.
That, my darlings, is the essential difference between these two episodes. Helen Raynor got both the guy and gal right - the guy afraid that physical deformity would ruin the relationship, the gal too much in love to care. Russell T. Davies, on the other hand, got the gal absolutely wrong. And he made Rose Tyler a little bit less of a character because of it.
The moral: men and women are similar, but not the same, and a writer would do well to always remember that. Make sure that when you're running your work by your Wise Readers, you're asking them to point up the bits where you got the other gender willing-suspension-of-disbelief shatteringly wrong. But also keep in mind that generalizations about gender differences are just that - generalizations. You can have shallow women and deep men when it comes to the whole body vs. mind thing. Real people aren't 100% stereotypical, and neither should your characters be. The most important thing is to stay true to the character you've built.
All that said, I'll forgive Russell T. Davies anything after what he did with "Midnight."