I don't decide someone's a bot based on how quiet they are or how many tables are open. Mind you bots generally don't talk, but when their masters show up to check on things they do. And when their masters decide they can outplay everyone at a table they haven't even been watching then lose a huge percentage of their stack, whoa baby do they ever have hissy-fits.
So I go by their general behavior in a game. What hands they play and how. Also their timing. Humans don't have that really consistent timing of tick-tick-tick-fold, or WHOOSH!-ALL-IN!
Humans use the little buttons. You know what I'm talking about, where u can decide your actions in advance. I guess they're called advance action buttons or some such. Point is they use them, so their folds are faster. Another thing I noticed is that generally a human's all-in is slower than a bot's. They act in reverse. A human has to mull over if they really want to risk all their chips on a hand. Bot's don't have to mull anything over.
I haven't the foggiest how long it takes for a bot to calculate which hands to play, but that might have a lot to do with their tick-tick-tick-folding. They do play a limited # of hands, and their behavior's very predictable.
At any rate, best thing you can do is try to get in the swing of the bot's behavior. It changes from level to level. All-in at the lowest level is basically 5 times the big blind a level up(I suspect that's why raising 5 times the BB works so well in freerolls
but have no proof). Also know that some are programmed to protect their blinds with certain hands(means u the human has to be extra careful when a bot's blinded).
Oh and don't show your hands. Even on it's worst day a bot's a great spy if nothing else.