Walls, ceilings, floors -- neighbors and sound

I've started to search around my little town for a condo, and I'm wondering, all other things being equal (which they never are, of course), what might be best for allowing me to do a good deal of listening without making my neighbors have to hear what I happen to be into at that moment. In general, do folks above hear more than those below? Or vice versa? Or is it a bigger problem for those on the other side of a shared wall? I understand that this will all depend on the construction of the place in question, but can anyone tell me if there are certain things to look for? And other to avoid? Thanks for any help you might give me with this one.
-- Howard