If no, how many times have you done it and have you won?
Only once before, and yes, I'm still amazed I won. I guess this year we'll find out if it was just beginner's luck!
If no, what is the best tip you can give to a first-time NaNo'er?
Best advice I received, and happy to pass it on, is to not delete a single word. Not a one. It helps at different levels: first, certainly, it helps towards reaching your target word count. But more than that, making the commitment with yourself of not deleting a-ny-thing helps to keep that Internal Editor under lock and key. By all means, mark up your text, highlight parts you know you'll have to change or check later, but Do. Not. Delete. Anything.
How much preparation do you plan to do before November 1st?
I'm a pantster, so preparation amounts to registering on the NaNo site, and updating my profile and novel info. Oh, and creating a new document in Scrivener. This year I actually went ahead and created the 30 chapter files; I aim for ~2K words per chapter, so ideally I write a chapter a day during November. But I have no outline, no real plot. I write literary fiction, so I guess plot is secondary to characters--praise be. All I have, really, is an idea I'd been playing around with for a few months in my head. Ah, and because it deals with homosexuality in Mexico, I googled articles and blogs on what it means to be gay in Mexico. That's pretty much it.
Got anything you'd like to tell us about this years project?
I may be in over my head. As I mentioned above, one of the themes is homosexuality in Mexico--how it's perceived, how society deals with it, how it affects people's lives. But I'm not gay, and due to the very issue I'm trying to address, there's no one I could interview, no one I know who'd be willing to a) admit they're gay, or if they would, to b) talk openly about such intimate details as at what point they realized their sexual preferences were different, how that made them feel, how their families reacted, what they learned at home about homosexuality that shaped how they perceive themselves beyond the mirror society imposes. That lack will certainly make the story suffer, because I aim my characters to ring true and organic. But I'll tackle it with my meager internet research and hope that by the time I get around to finishing the novel (even assuming I win, 50K is a bit less than half of a first draft for me), I'll have access to trustworthy sources to enrich it.