Devon Barlow is a headstrong young man nearing his twenty-first birthday. He’s highly intelligent, very physically active (he goes spelunking on Pluto, how cool is that?) and he has a strong suspicion that his parents might just be pirates. Save for brief forays on Mars or Earth during the holiday seasons, Devon has lived the bulk of his life on board Zephyr, a hauler-class space ship.
I am a thirty-something single mother who reads too much and spends an embarrassing amount of time on video games. (Hey, games help keep my creative brain fresh and stuff. Don’t judge.)
So how does a thirty-something single mother find the “voice” of a twenty-year-old boy in order to believably display his character on the page?
Well … I read a lot.
I did say I read too much, didn’t I?
In this case I deliberately hunted for books with young male points of view (really not that hard to do, you can find them in just about every book you pick up) and I studied them. I looked at what they thought or felt or did differently from how I might have reacted in any given situation and I jotted it down in a notepad.
I also talked to guy friends. If there was a situation happening on Zephyr in the book that could be easily translated into day-to-day life, I would nudge a guy and ask; “Hey, when you were twenty what would you have done if …”
Disclaimer: These friends know I am an author. They find it highly amusing when I quiz them about what it’s like to be a dude and are more than happy to help out. However … most of them still think I’m crazy so … do this at your own peril.
That said, Devon Barlow might be a twenty-year-old young man but he is also a human being. He may think and feel differently from me but that does not mean I cannot relate to him. (Except for the pirate thing. I never suspected my parents of being pirates.)
Fiction is the place where we can mind-meld with the world around us. It helps us understand people precisely because we find ourselves relating to characters vastly different from us. It teaches us to look at the core motivation in people because we know that, male or female, that motivation is what’s going to define them as a person.
So!
How to write a dude when you’re a girl?
1) Read. (You should be doing this anyway if you’re a writer.)
2) Observe and/or ask your guy counterparts.
3) Find the core motivation.
… and if anyone else has tricks to writing the opposite gender I’m happy to hear them. I’m sure I missed a few.
AJMaguire 
When I write any character, I consider details of their background. What life events have shaped them, and how have they reacted to those events? What is their personality? What society are they living in? All of these things will have a bearing on a character.
One story I’ve tinkered with for many years has two important female characters in it. I guess to a certain extent I’ve based them loosely on women I have known, which helps me to flesh out some aspects of their character, and then throw in some of the weird stuff I have going on in the world. I’ve not thought about asking female friends (but then I don’t tend to discuss what I write).
Making me think about it is interesting, I haven’t really examined the process before. I don’t believe I approach writing a female character any differently than I do a male character (or an alien character for that matter). I tend to approach it the way I approached role-playing (the games, not the other sort). Take on the persona of the character, and then consider what their reactions would be.
What I have realised is that the most challenging character I find to write is one from a different (real) culture. From dealings I’ve had with people from other cultures I’ve found they sometimes react in ways I don’t expect. I have the advantage of working in an ethnically diverse office, and I’ve been able to discuss some of these situations, and discovered that culturally people are conditioned differently. Most of my exposure is to western culture, so I tend to drift automatically to those settings, writing characters who have a western perspective.
Oh! I know what you mean. During my Cultural Anthropology class I learned quite a bit about how my culture has shaped the way I view the world. It certainly shapes the way I write about the world, too. Things slip in that you simply don’t realize are a product of your own upbringing.
Like how you peel a banana, for example. The “top” of the banana to me is actually the “bottom” of the banana when it’s growing on the tree. But here at my grocery store we stack them upside down (apparently) and so we’re not used to seeing bananas in any other way.