Many newsgroups post newbie-only offers by veteran traders who wish to distribute copies of a show without the hassle of setting up a tree. It's a good idea to read a newsgroup for a few days to get an idea of what's acceptable in the group before posting. One way to ensure being ignored or even flamed is to violate some basic tenet that would take seconds to learn. Once you connect with a trading partner, it's also a good idea to start slowly, two or four tapes at a time, to make sure your standards are similar and the trader is reliable. The Internet has been likened to the Wild West with no sheriff - you're basically trusting people you've never met and you don't have much recourse if things don't go well.
Good communication is the key to successful trades.
Also be prepared to wait sometimes up to a month or more for tapes from trees and indvidual trades. Some traders are quick, while others get in over their heads running too many trades at one time. The whole procedure is relatively inexpensive. Overall, the system works well. With a little commitment, patience, and perserverance you could soon be happily receiving envelopes full of live music.