Once you've learned to interpret a player's betting patterns, try to figure out how his personality traits might reveal the kinds of poker decisions he will make. Focus on poker fundamentals first. Then learn to get inside other players' heads and use the information you gather to make solid decisions. Here's how to do it.
When you watch me play on television, you'll notice that I engage my opponents in conversation by asking routine questions: Where are you from? How long have you been playing poker? Do you play on the internet? What do you do for a living?
Every answer reveals a little information that helps paint a picture of who they are and how they play. Asking these questions is the first step in reading people.
Sometimes you'll notice obvious character traits. A brash person, for example, rarely plays poker conservatively. He's far more likely to play a lot of hands and play them aggressively. A soft-spoken person, on the other hand, will usually play cautiously.
Another important consideration is what your opponent does for a living. It's what I call The Lawyer vs. the Sunday School Teacher syndrome.
Play against a lawyer and you can safely assume that she'll be smart. Her profession requires that she's able to spin a tale in order to win a case. Well, in poker, that's called bluffing! I consistently find that lawyers are apt to play their hands in a tricky fashion. They really do tend to be big time bluffers.
OK, how about the Sunday school teacher?
Well, you can be reasonably certain that lying isn't in their nature. And while bluffing an opponent out of their money isn't exactly lying, the act of deceiving another player might be more difficult for this type of player. The truth is they're often conflicted about bluffing. So when a Sunday school teacher makes a big bet on the river, you'd better think about folding -- unless of course you've got a monster hand yourself.

