Writing in CNet, Declan McCullagh exposes the kinds of consumer behavior that can bring the unwanted attention of RIAA's sleuths and law suits. This useful article covers shared folders, large collections of tunes, open wireless networks, and choice of P2P applications:
The RIAA has focused on copyright infringement on the more visible, centralized services such as Kazaa, Morpheus, and Grokster. It hasn't focused on file sharing through instant messaging or closed P2P networks. The more obscure the P2P network, the less likely it is to be monitored.