The NY Times has an excellent list of What to Do on Election Day. In particular:
Your board of elections can tell you where to vote. If you can’t reach the board, a nonpartisan hotline, 1-866-OURVOTE, has a polling place locator. So does the Web site www.mypollingplace.com.
No voter can be turned away in any state this year without being allowed to vote. If there is a question about your eligibility, you must be allowed to vote on a provisional ballot, the validity of which will be determined later. But if you are entitled to vote on a regular ballot, you should insist on doing so, since a provisional ballot may be disqualified later on a technicality.
If you experience problems voting, or if you see anything improper at the polls, you may want to get help. It is a good idea to bring a cellphone, and phone numbers of nonpartisan hotlines like the Election Protection program’s 1-866-OURVOTE and Common Cause’s 1-866-MYVOTE1.
As long as you are in line before the polls close, you are legally entitled to vote. Do not let poll workers close the polls until you have voted.
So put those numbers in your cell phone and don’t leave until you’ve voted.