i am not trying to steer people away fro eccie, but there is an informative forum site called lau xanh. which lays out the lay of the land in vn from the the experiences of forefingers who do business in vn day to day, tourist, and hometown people. unfortunately i do not know how to read viet, but there is a section in there were actual foreingers talk in english about their experiences in vn and in my opinion read up on it and learn it. stay your ground on the price for massage places in vn its usually a set standard and they will try to deviate you from it. i find the philippines much more accomodating than vn.
ps: do not try to meet girls through karaoke method. if a "tour guide" on the street try to take you karaoke you better be fuckin rich and have patiences to wait out an hour up there. otherwise just have them take you to the hotels. normally at those places its probably 4/10 i rate, bar girls are much better than the ones at the hotel already.