before you buy an specialized book concentrating on low limit hold em, or something similar, buy a true beginners book like, The Idiot's Guide to Poker, etc. This will get you familiar enough because most of the already recommended books assume you know the game at least a little bit. they will sound foreign to you if you dive right in. what kind of advice i give depends on your actual experience. have you ever played home poker? do you know the hand rankings? know the basics of hold em, stud, or draw? do you know any odds, or anything about pot odds? i suggest starting out with very basic books and when it's apparent that you're above them then move on to more complex literature. it can't hurt too much to play at an internet site for free to get the hang of the procedures, but don't get used to it because play money is a very different situation.
once you get through all that, here are some valuable tips IMO
1. learn the starting hand charts and why they are set up like they are. understand that when you play weaker starting hands than your opponents, your bankroll will suffer. so play tight

2. listen to what other people say and judge for yourself whether or not it's good advice. think about their recommendations and why it may or may not work, then you'll begin to analyze the game more.

3. control your emotions at the table

4. be prepared for losing sessions, nobody wins everytime.

5. learn from your mistakes and improve your play

there are tons more tips you'll find in books and online, check out this site too for some basics,
www.pokertips.org

hope that helped a bit