Weekday or weekend? If the former you can usually get good seats at the web site this far in advance. Weekends, particularly mid-season, go quickly (although I was able to get surprisingly good seats for the Dodgers series when they went on sale a few weeks ago), so Stubhub or SeatGeek are probably your best bets.
One piece of advice - before you buy go to preciseseating.com and check the view. That’s particularly important if you are in the grandstand sections where poles can block your view. The Sox’ definition of obstructed still leaves some seats with, at best, marginal views, being sold without warning. Preciseseating.com will show you exactly what, if anything, is obstructed.
