it is really not that hard
basically
choose juliet related options to get to juliet route
choose aspen related options to get to aspen route
when in you're in one of the routes, choose whatever and you will get one of the good endings
and then choose the opposite every time to get the other good ending
also doesn't matter if you go to the kid on cuba st or the guy at waterfront
but I do recommend always going to one of them for 1 playthrough and always going to the other on the other playthrough