As Arjonius said, the way you should play your Jacks varies with some factors beign:
- table position
- the relative size of your chip stack
- what has happend, if anything, before the betting gets to you
- what the other players at the table are like
- your tble image if you feel you've established one
With a good stack I always open to 4 or 5 times the BB, if someone calls its becouse he has a pair or something. Most people with QQ, AK, AQ or AJ will call you. But the people holding AA or KK will go all in. This is your time to go out.
Also check the board for any AKQ, thos cards can ruin your pocketed Jackies.
I always try to change the way I play and I slow play those jacks most of the time. If a jack cames in the flop, you lucky B...ard have a nice trips or better.