Sklanky on Early Position Fishhooks

Sklansky's strategy on pocket Jacks:

One hand that we have not yet addressed is a pair of jacks in the pocket. If no one has opened and you are in an early position, it is usually best to raise with JJ in a tight game and to just call with it in a loose game. With two jacks you would prefer either to have no more than one or two opponents in the hope that your hand holds up without improvement, or to have as many opponents as possible when the majority of your profits come from flopping three-of-a-kind. The worst scenario is when exactly three or four opponents see the flop with you. This most likely would occur if you called in a tight game or raised in a loose game.

If you hold JJ and the pot has been raised and reraised before the action gets to you, you should fold. This is correct even when you are in a middle or late position. However, if you have already opened with JJ and the pot has been raised and reraised behind you, then it is correct to go ahead and call because of the pot odds. What
you are hoping to do in this situation is to flop trips. If you do not make a set, be prepared to fold (although folding is not necessarily automatic).