Not sure where to vote? Go to http://maps.google.com/vote
Not sure what your rights are as a voter, state by state? Go to this ACLU page. Print your state's Voter Empowerment Card and bring it with you.
If you get to the polling place before the time the polls close, you're entitled to vote. Don't leave.
Don't wear or otherwise display a candidate's name on your clothing, a button, etc. It could be considered campaigning within 100 feet of the polling place, and you might not be allowed to vote.
Please vote. Then go get your free Starbucks coffee! Worth every penny...