It has been my experience that if you have TPTK and are called down to the river and check it, someone else who has TP will check it down with you. If you are smooth called twice after making good sized bets and then are faced with a large bet into you on the river it is likely correct to fold more often than it is to call. If you have notes on how a player plays when the slowplay their hands that helps.

If you check at the river, most of the times youre going to have to call if he bets (depending on the size of course). You are inducing a bluff there and you need to call alot of the time. Most people will raise the turn if thy have you beat.

What about a blocking bet?