Yeah, I agree you can't count on some one's profession as the end all, be all of tells, but surprisingly a lot of people, or even most people, either are that stereotypical or conform to the stereotype. I learned this lesson from a Russian stripper while she was dancing her way thru' Med School, if you ever get the chance to date a Russian girl do it, they're a rare breed of beauty, intelligence and moral ambiguity. She could figure out who her customers were and what they wanted just by their appearance, clothing, "innocent" conversation and lowering their inhabitions. Clearly I don't haver her assets when it comes to lowering men's inhabitions, but alcohol is a fair substitute.

Point being, as soon as some one sits down at a table, be friendly and get to know them, buy them a drink and let them get to know you. Find out where they're from, find out what they do, find out whether or not they have a house, car wife/girlfriend, kids and even who they're favorite sports teams and players are. While you're doing this, take a good look at them; sun glasses, ear rings, necklaces, watches, suits, T-shirts and shoes will all tell you a story about that person. People in the 30+ range tend to be way, way more predictable than people in the 20+ range, largely because they've either figured out who they are or have established themselves. Hustling a home game or even a small city/town casino is really a lost art, and people who work in the service industry, it doesn't have to be an exotic dancer, any bartender or waitress will do, know they're clients like the back of their hand, so learn to see what they see.

If you think you've already mastered this, then here's a simple/not so simple test, if you can go to a rodeo, cattle auction, farmer's market etc. and pick out which of them is rich and which of them is poor at a glance, then you've developed an absolutely sick reading ability.