I totally got disenfranchised (aka: I am dumb)
 

ME: So, how do I write in a candidate?

CLERK GUY: *awkward pause* We don't do that.

Welcome to the heart of Texas. Cross out one vote for Ralph Nader.

Oh well. I don't know exactly what my rights were in that situation (ie, this is probably my fault and I should've planned ahead, should've seen it coming, live and learn), so I floundered and flip flopped and spent what probably seemed like a worrying amount of time in the booth before picking Kerry.

Honestly, I don't really like the guy that much, but I can't honestly say I go for Libertarianism and I'd probably be in the bathroom puking right now if I flipped the Bush switch. I gave a little thought to not voting for the president at all, but it seemed like a long drive just to vote on the state house. So I just came out of the thing with sort of a bad feeling in my gut.

Well, Bush is getting my electoral votes anyway, so I probably shouldn't sweat it too much.

To write in a candidate, you write the name on the ballot if there is no space for it.

It was a mechanical thing with levers. If there was anything I could've written on I assume the guy would've given it to me.

you're state might not allow write-ins--they're typically not counted unless the race is close enough for a recount anyhow...

Well, from a fellow supporter of Nader, you can have consolation in the fact that your vote will be counted as part of the popular mandate that tells Congress not to fuck around with our new president and illustrates to the rest of the world that the US isn't full of nutters.

on my polling machine there's a sliding door to the left that you slide open and there's a pencil which you can use to write in your vote.

I've done it all the time for years in CA, NJ, and NY.