You should have just laughed like the guy was joking with you. Looks less guilty, and less nerdy (casinos think most card counters are nerdy). Dealer might have actually been joking.


Assuming he wasn't joking, and he wasn't a counter himself, then you're doing something really obvious that gives it away. Lips are moving, staring at the cards, playing your hand really slow, etc. This can be fixed by practicing until you can count more quickly and look natural.