There are a number of ways to tell if you are counting cards. Once the casino is scrutinizing you, the only defense you have is to get up and leave.
The trick is to not get the casino to scrutinize you. That means you have to look like a sucker. How do you do that?
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[li]NEVER jump your bets quickly. Nothing is more suspicious than a player who always starts a shoe with minimum bets, and then either walks away or bets big towards the end of the shoe. That’s pretty much the ‘signature’ of a card counter.[/li][li]Don’t sit at 3rd base. This is the favored position of card counters, because they gain a tiny extra advantage by seeing more cards before having to act. The added scrutiny isn’t worth it.[/li][li]Be friendly, and tip reasonably. The surest way to get get attention is to make a big hairy thing of yourself when losing, or standing on your ‘rights’ when they don’t want to let sit in the middle of a shoe, or whatever. Most of the guys I know who were barred for card counting were also jerks, and the casino was just looking for a reason to punt them.[/li][li]Don’t bet large. This obviously doesn’t apply to pros, who need to bet reasonably large to make a living. But if you’re just looking at making a bit on the side or going to Vegas without losing your shirt, keep your bets reasonable. The typical casino couldn’t care if you’re counting, as long as you’re only spread from maybe $5 to $50 or so. But the minute the green and black chips come out, the pit will take an interest in you.[/li][li]NEVER play for a long time at one casino. If you play long enough, someone will start watching you at some point, and then you’re cooked because the key to card counting is to bet big when the shoe is rich in tens and aces, and bet small when it isn’t. There’s no way you can hide the fact that you’re playing a winning game if some guy who is also a counter is following your play from the eye in the sky.[/li]
The rule of thumb is generally 45 minutes in one place, then pack up and go elsewhere. Or, if you hit a hot shoe and are forced into some unusual plays (either betting big, or doubling a soft 19, or something else equally suspicious), then get up and leave as soon as the shoe is over. As a professional counter, that was the worst part of the whole deal. The continual moving from casino to casino, looking for good penetration, avoiding pit bosses who know you, etc. BORING.
[li]Avoid the ‘card counter profile’. That typically means a youngish male, betting money that it doesn’t look like he can afford, carrying a serious expression, drinking bottled water, etc. If you’re betting big, look the part. Order a vodka tonic or something while the pit boss is within earshot, then carry it with you to the bathroom in a while, dump it out, and fill with water.[/li]
[li]Be VERY good at card counting. I survived a number of close inspections simply by being able to count so fast that I could ‘snapshot’ the table out of the corner of my eye and continue playing while in a conversation with the pit boss.[/li]
[li] Avoid high profile plays, like splitting tens, doubling soft 19’s, etc. You give up almost nothing by ignoring these plays, while making it much more difficult to spot your skills.[/li][/ul]
There are a lot of other tricks. For the best information on this aspect of the game, I highly recommend two books by ‘Ian Anderson’ - “Turning the Tables on Las Vegas”, and “Burning the Tables in Las Vegas”. I know “Ian” somewhat, and this guy is one of the most successful high-limit card counters around.
Counting cards for pocket money as a hobby is a lot of fun. Doing it for a living is a GIANT pain in the ass, unless you’re happy making minumum wage. If you want to make a good living (say, $75K a year or more), you’re going to be travelling. A lot. It’s a ton of work, lots of risk (I know good counters that have had losing streaks so bad they were down money at the end of a year), and it gets boring.
I didn’t stick with blackjack all that long once I got to the higher limits. I found out that Poker was much more profitable, much more fun, and it was nice to have the casino actually happy to see you.