I appreciate all the responses!
For cocked dice I've been taught the method is to place another die on the top face and if the die rolls, then reroll the die, if it stays, then its solidly on that result.
Does anyone else use this or another method to check?
Never done this. If I get a cocked die, I point to it and ask my opponent if he wants me to keep it or reroll. Sometimes it's obviously cocked, and sometimes it's almost flat, but I like to give my opponent some input before I pick it back up again.