The post at this blog is more concerned about Republican efforts to challenge voters in predominantly democratic precincts, but the information they provide is very useful for anyone Republican or Democrat. It gives good information about what steps to take to reduce the chance of problems at the polling place and what to do if your right to vote is challenged or if you encounter other problems.
The thread includes a link to this site that lets you enter your street address and zip code and returns the correct polling place for your precinct and information on what type of ballot system is used for your area.