that "most" counters would not be noticed by you, based on demeanor at the table. The primary way I pick up on a "fellow counter" is bet correlation. If we are both going up and down almost together, I usually leave the table so that it isn't as obvious. I can't recall seeing someone that made me think "jeez, he's an obvious counter, serious, watches the cards like a hawk, moving his lips to count, having to think about his bet or playing strategy.
I played one game in Laughlin this past summer, where I got a _very_ fast dealer and asked "want to see if we can set a world record on hands played in 15 minutes?" She said "sure" and called the pit boss over to count hands. After about 2 minutes, as everyone was chatting, he dropped the "this is a good example of a good player that can't possibly be counting cards, I don't even see how he can decide whether to hit or stand so quickly, much less keep up with the count, the true count, and so forth." :)
Of course, if you play enough, you can decide "hit" or "stand" without even having to add up your hand, there are just not that many different combinations of cards. BTW we did just over 60, and the only thing that slowed the game down was the dealer completing her own hand and then paying off or raking chips. Sometimes took her longer to add up my hand to decide whether I had won or lost than it did for me to calculate my bet, get the chips out, and signal hit/stand/double/split and complete my hand(s). :)
BTW, during all this, I carried on a conversation while the dealer was "doing her thing" ignoring her cards until the last second, etc. You don't have to look stupid to not look like a counter. :)