A good way to help yourself learn ASL is to get yourself a copy of the American Sign Language Dictionary, by Martin L.A. Sternberg. There's even a multimedia edition available on CD-ROM which makes the drawings easier to interpret.
The book was originally published in 1994 (HarperCollins Publishers, Inc) and has since been revised. It contains over 6,600 illustrations and 4,400 signs -- certainly enough to get someone started. It also houses the simplest and clearest illustrated version of the American Manual Alphabet I've found. Once you get that down, you can sign any word you can spell...which comes in handy when you get stuck in the middle of an ASL conversation.
The author is a faculty member at Hofstra University and Adelphi University. He's been deaf since age 7.