They rotate divisions every year, For example in 2008 the AFC East plays the AFC West and the NFC West. Those 8 games plus 6 games in their division equal 14, The other 2 games are determined by order of finish, NE plays the first place teams in both remaining AFC divisions AFC North and South, that'd be Pitts and Ind. Buffalo plays the second place teams etc. Pretty easy to figure who's playing who years in advance.
Keep in mind that the strength of schedule is obviously based on the previous year. There's always a chance that a bad team from the previous year will wind up being pretty good.