I could more or less be considered to be on a type of paleo diet. The biggest thing is to avoid grains. I'm currently reading the Primal Blueprint and it is a pretty good book, not to heavy on the science but it really shines on the practical aspect of doing the diet. I've heard that Robb Wolf's book "The Paleo Solution" is heavy on the science if that is what you are into. And Dr. Loren Cordain just came out with a new book called "The Paleo Answer" which is a follow up to his original book "The Paleo Diet". From what I understand the original "Paleo Diet" isn't as well regarded as some of the newer books since this whole 'movement' is evolving the newer books contains the latest research.
The biggest thing to know about the paleo diets is that they are based on science. However much of the nutritional science is deeply flawed, so where current science doesn't provide an answer they look to what we know of paleolithic man for clues.
"Eat as if your life depends on it!"