i'll tell you what i did though i'm sure there are about 100 different ways to do it.
first of all, i didn't know this when i applied so i'll just let you know. when you rank the 2-3-4 programs, for each program, you can list a separate prelim/trans rank list...
so if your number 1 is bu, you can list boston area prelim/trans and your number 2 is gwu, you can list a different rank list for prelim/trans programs.
of course, that just increases the number of prelim/trans you have to apply to. in the end, i only interviewed at prelim/trans places in the city i went to med school. i figured if i matched at a 2-3-4, i would just stay one more year in philly, then move. of course, if you're trying to plan your life around a significant other/family/etc, it can get more difficult.
i applied to somewhere between 25-30 places. i think i got 18-20 interviews. i interviewed at 16 places, ranked 14. i also interviewed at 6 prelim places. lemme tell you, it got tedious real quick. looking back, i can't believe i even made it through so many interviews. if i were to do it all over, i wouldn't have applied to 2-3-4 programs for two reasons. one, the extra year or residency isn't worth it, two, if you're doing an extra year, wouldn't you rather do it in EM rather than be IM's scutmonkey. i have friends in trans years now who are going into ophtho, anesthesia, etc, and hate it. but see, they HAVE to do a year, whereas we don't... but , unfortunately a lot of 2-3-4 programs are strong and so you have to go through all this pain.
again, i think interviewing at 16 is a lot, even excessive. most people will rank in their top 3. but i think if you have a rank list of 10-12, for the most part, you should be all right. the other viewpoint, however, is you might as well suffer and interview at all places b/c stats are stats and you don't want to be the one person who got screwed -- ie ranked 12 places and didn't match at a single one. i mean, if you interview at all places and rank all and then don't match, you won't have any regrets about cancelling.
i guess i haven't told you much except given you some things to think about. good luck.