1. Subscribe to Publisher's Weekly…or at least visit their Web site often.
2. Attend seminars and conferences that host agents, editors, and publishers.
3. Haunt literary Web sites and subscribe to e-newsletters for freelance writers. And the best, cheapest way of all…
4. Become your librarian's best friend.
To elaborate on No. 4, you can at least become her best and friendliest customer. My local librarian knows I write. When she's buying new books she keeps me in mind as she reads through the lists of recently released titles. Hello! Can you say "research assistant"? For free! Books are these people's lives. They are walking universities on the marketplace, and it's not hard to draw them out of their paper shells.