A mixture of helpful women friends and a lot of early failures. I’ve found the biggest problem with writing the opposite gender comes when you add them simply be a love interest. Nobody is just a love interest in their own minds. Make them a character first, a plot device second.
I should probably back up and point out that I wasn’t always good at this. In fact, in the first few books I wrote before ELANTRIS I was terrible at it. That disconcerted me because it was something I wanted to make a strength in my writing. This is partially due to the fact that so many of my favorite fantasy novels growing up, when I first discovered fantasy, were from female writers with really strong female protagonists. So there was a piece of my mind that said having strong female protagonists is a big part of fantasy. I don’t know how common that viewpoint is, but because those were the people whose books I read—writers like Anne McCaffrey, Melanie Rawn, and Barbara Hambly—I wanted to be able to do that in my own fiction. Even beyond that you want every character you write to be believable, and it’s been a habitual problem of men writing women and women writing men that we just can’t quite get it right, so I knew it was going to be something I’d have to work hard at.
I took inspiration from women I know, starting with my mother, who graduated top of her class in accounting in an era where she was the only woman in her accounting program. She has always been a strong influence on me. I also have two younger sisters who were a lot of help, but there were several friends in particular who gave me direct assistance. Annie Gorringe (who was a good friend when I was an undergraduate—and still is) and Janci Patterson were people I sat down to interview and talk to in my quest to be able to write female characters who didn’t suck. I would say specifically that Sarene from ELANTRIS has a lot of Annie in her, and Vin from MISTBORN has a lot of Janci in her. In WARBREAKER, Siri and Vivenna don’t really have specific influences but are the result of so much time working at writing female characters that it’s something I’m now comfortable with. (Their personalities arose out of what I wanted to do with their story, which was my take on the classic tale of sisters whose roles get reversed.) It’s very gratifying to hear that readers like my female characters and that the time I spent learning to write them has paid off.