I was going to tell you to just buy the cheapest ticket then sit wherever you want. Since the Red Sox are dropping out of the playoff race quickly, there should be a number of empty seats at many September games. I'm going to see them play the Twins the week before, and that's my strategy.

However, Yankees will likely be a different story. Best value is probably going to be in one of the Grandstand seats. Though of course if you want to spend more there are plenty of options. Bleachers are cheaper but too far away. If you're in the grandstand, double check that you are not going to have an obstructed view. Use this site: http://www.headspinsoftware.com/red-sox-fenway-obstructed-view-seats.html. If you see a seat for really cheap, it's probably because home plate is hidden behind a pillar when sitting in that seat.

Transportation will just depend where you're staying. The T is cheap and easy, though there are lots of people. If you're staying in the city or near a subway stop, just do that.

Don't really know on food. There are bars right next to the stadium and plenty of restaurants a short walk either way.