The Caro book is the bible on such matters, but the one thing it absolutely cannot do is make you understand people. Reading people in my opinion is really a gut instinct. Sure there are little things you can look for, nuances you might say, but when you peel away all the layers of the onion, you must rely on your ability to feel what the other person is putting out even though he is doing his best to keep his real emotion or intention hidden.
Before the visible, know the things you can glean difinitively. Keep a runing record of what cards people show down and how they bet those cards on every street. Memory is vital when you aren't playing online and can't take notes. You must remember these things for every player. Devise some kind of system for yourself, it helps me. I categorize hands by strength so I only have to remember 4 or 5 different classes of hands instead of tons of starting hands individually. Then all you have to do is remember monetary amounts. Playing limit this is a little easier to do because you can just remember the number of bets. For example Q-J is a rank II hand and the player in seat 3 always plays rank II hands cautiously, limping in to see a flop. I hope this is making sense. Also keep track of betting patterns.
It bears repeating that a very weak player will usually act strong when on a bluff or draw and meek when holding a made hand. This is the really simple stuff but you would be surprised how often it holds up. Just don't rely on it 100%. Something I absolutely love is when someone wears sunglasses at the table. When wearing them, in my experience, people tend to feel hidden and will gesture more with their body and make facial expressions more often. When you are staring someone right in the eyes, they are more congnisant of their face, facial expressions, and body language.
When the flop comes down, watch the opponents left in the hand, not the cards. The cards will still be there in 15 seconds, their reaction to the cards will be long gone. After the flop if a player looks at their hole cards again and stays in the hand, it usually means that they are making sure they have the hand that they thought the had, a sign of strength. Now you watch their bet to see how strong they are.
Watch peoples posture closely. Poor posture and aggravated body language usually disappears when a good draw or flop hits them. Also pay close attention to their hands when they place chips in the pot and how the place them.
Also, if someone wants to talk after they raise, needling you and antagonizing, let them do it. Much can be learned from someone who can't shut up. Taunting and bold statements generally mean they don't want a call and silence from a loudmouth generally means strength.
After all this is considered, you simply have to rely on your gut instinct. It doesn't always pan out for you, but I find I have a fairly uncanny knack for being able to smell a rat. You simply cannot teach someone to read others, but one can learn on their own. There are a certain number of "types" of people, once you can categorize people, they then become easier to read. We are creatures of habit and will do the same things or kinds of things in certain situations almost without fail.
One other thing I recommend is that when sitting down for the first time, basically sit out for the first half hour or so except in the blinds for cheap or free with a decent hand or with a premium hand anywhere else. Don't play anything but the top 4 or five hands, just sit and watch. Watch every single move on the table. If there is someone there that hasn't made a move in the first half hour or so, he is a rock you can almost bet on it. Good luck, and let us know how you do.