You are eligible to vote if you were a member of last year's Denvention, or this year's Anticipation in Montreal. If you don't have a membership in either convention, then you'll have to get cracking and buy an Anticipation membership toot sweet!
Once you've got your membership, you can go to the Hugo page and download the appropriate forms, or vote online.
Here what to vote for.
Implied Spaces, by Walter Jon Williams, Night Shade Press, July 2008.
"Pinocchio," by Walter Jon Williams, The Starry Rift, ed. Jonathan Strahan, Viking 2008.
You can nominate anything you like for the other categories, but if you nominate anything else for the novel and novelette categories, please make sure they're works that don't have a chance in hell of winning. Thank you!
I know I can count on you guys. We've been through a lot together, but I just know that if I can get a couple Hugos, all the wretchedness and misery and neglect will seem like a faraway dream.