Cheating casinos

Hi everyone,

I'm curious about cheating casinos and I have two questions.

1) What is the most common way they cheat. Taking a wild stab I would guess it is by removing the tens and putting in 3s 4s 5s and 6s. Not too earthshaking a guess but could anyone help me more precisely on what they may do?

2) What is the best count to detect cheating?

Cheers.