"How do you write women so well?"
"I think of a man, and I take away reason and accountability."
-As Good As It Gets
It is in the spirit of gender equality, that I say women can't write men either. Or rather, women who do a good job of writing men can still fall short.
I tried to read My Sister's Keeper, but I was so put off by Picoult's absurdly written lawyer, I nearly threw the book across the room. There was no way anyone could convince me that this was a real human being. However, Carolyn Parkhurst with The Dogs of Babel has written a protagonist that is not only believable as a human being, but you might even get the sense that you have met a guy like him before.
There are a couple of issues at work here. First, you have to understand the human condition enough to create a believable human being. Second, when it comes to anything that modifies a character beyond just being human, you have to focus on perspective.
Full disclosure, Ali really is a woman, and I really am a man. I also happen to be over a foot taller than her. Now, just from a physical standpoint, she has the advantage of seeing things on the bottom shelves of the bookstore where I possess the advantage of seeing the things on the top shelves. In this case the key to understanding each other's perspective is to either squat down or learn how to build a ladder.
There is another issue at work here: Double Standards that often get ignored. When a man "can't write a woman," he is viewed as inexperienced in talking to girls and is to be pitied or ostracized. When a woman "can't write a man," it's because "men folk are just too confusing to understand." Which I find particularly amusing, because men generally aren't a very complicated group of creatures. If you can't figure them out, I challenge you to reassess how much you're really paying attention.
Also, it is a fundamental fallacy to assume that the experience of a group is completely homogenized. Just the fissures between feminists regarding how to fight for equality is enough to know that if you're going "to talk to women," you're best served talking to a variety of women. I've met Stepford Wives with some of the most awful, degrading opinions of men, and granola hippy feminists who are able to tick off rather unique things men have to endure, and respect men for doing so. You have to make sure you've got your newly acquired perspective in perspective as well.
Basically, it comes down to the same things you have to keep in mind with any topic you wish to write about. Do you due diligence, stretch your imagination to include a perspective that doesn't come naturally to you, and make sure you're not building your ladder wrong. This is not anything new, regardless of the topic.
As for all of this talk of women depicted in chainmail bikinis: Yes, they're impractical. Yes, they are probably uncomfortable. But, the goal of putting a woman in a chainmail bikini is NOT to present a believably strong woman. Fun Fact: A character called Jirel of Joiry was written in the same era as Conan the Barbarian. She was written to be just as physically strong as a man, and wore armor, but it was always worn with practicality in mind. She was the creation of a writer called C.L. Moore, who also was a woman. However, if you look at the cover of Weird Tales where Jirel first appears, she is in no way dressed as she was in story. She wore something more befitting an alluring damsel in distress.
Here's why women get dressed up in chainmail bikinis and are forced to stand in ridiculously uncomfortable and awkward positions: All of that work makes them look AWESOME. Men who see a woman in a chainmail bikini are more likely to spend money on whatever creative vehicle is being advertised with a woman in a chainmail bikini rather than a regular bikini, and especially rather than something practical. Some businessman took biology and eventually discovered the connection between spending tendencies and how they are tied to evolutionary-borne instincts that are steeped in how humans go about looking for a reproductive mate.
In other words, sex sells. But, it's not always the writer's fault that their characters are being tramped up. If you're going to take issue with that, take it up with marketing executives and book cover artists first. If they blame the writer, then you know where to go next.
And just for the record, C.L. Moore's depiction of men was fairly thin and one-dimensional as well.