All you've got to do to enter is put your info in over on their site -- the Grand Prize winner will pick up an all expenses paid trip to BlizzCon, and ten other winners will get some WoW-related gear from the contest's sponsors (SteelSeries makes the Zboard, and apparently they're releasing one for Wrath, so you might get one of those as well). There is a checklist that you can leave unchecked to supposedly keep the sponsors from contacting you, so even if you don't want your info opt-ed in, it looks like you're in the clear.
If you do enter, good luck! (And if you win, we'll see you at BlizzCon!) There are bound to be a few more of these contests showing up before the big event, so even if you don't walk away with a trip from this one, stay tuned.