This is the key. If you observe the people sitting at blackjack tables playing, you will see dozens of repeated physical characteristics that just about every single player does. If you listen to conversations at the tables, you will also hear many of the same things repeated over and over again without fail. Its a case of being exactly like everyone else to hide in the open.
For example, I'm walking by a table that seems full, I notice someone is coloring up so I slow up to possibly take their place. The person leaving pushes their chips towards the dealer, looks at their watch, makes a comment on how his wife is going to kill him for being late to meet her, he chugs whats left of his drink leaves the glass on the table, wishes the table good luck and leaves exiting from the left of his seat. Since I see an opening at the table I ask the rhetorical question, anybody mind if I take this spot? Usually everyone either agrees or doesn't care as it will keep the flow the same, but it doesn't really matter I plan on playing regardless. Anyway when I sit down I now know everything I need to play this shoe and even the next. Care to take a guess on what happened? This is by far not a typical situation, but an example how you can get a load of info without doing anything different from anyone else playing this game. By the way, these signals are not used currently by us so I am giving no secrets away.