Good tapes really work, and in fact, there's no substitute for them (except marrying a native). So, what's a good tape? To begin, you need a lot of tapes. If you look at a Berlitz book in a bookshop, you will see they have not that many tapes, but on the other hand, Pimsleur or FSI do have dozens of them. Second, what you want are either plain oral drills, or, better, situational exercises like in Pimsleur tapes. If all there is on the tape is a couple of dialogs, it'll be like learning to drive without actually getting behind the wheel. You want your tapes to make you participate, talk back, and for a long time. If they don't, don't buy them.