The first thing you need to know is that the Red Sox beat the Yankees tonight! Woo-hoo, go 'Sox!
Seriously, though, if you don't plan to spend much time in Boston (always out on trips), then a place near the T (the subway) is vital. Cheap dependable transportation that serves a good portion of the city, how could you go wrong there?
You might want to pick up a 1 month membership to 'Crashpads.com'. I've never used it myself, but I've heard good things.
Boston is an expensive city, so it's best to share a place if possible. Living outside the city is an option, but the metro area is known for it's terrible traffic, and often forces you to plan for traffic that may never materialize in order to ensure an on-time show at BOS. Hence why I recomend using 'the T'.
Good luck, and go 'Sox!
-Boo!