Polls are open 7 am to 8 pm, statewide.
To find out where you vote, and to see your sample ballot, fill out the form at
http://WhereDoIVoteMA.com .
As a result of the 2010 census, boundaries of wards, precincts, and Congressional and state legislative districts have changed this year. So even if you think you are sure where you vote and who's on your ballot, check it at that link before heading out to the polls.
ETA: there's some more very useful information at
http://davis-square.livejournal.com/3050558.html .