It depends a lot on the tournament. There are some tournaments that even if you raise preflop it seems that you only attract more players, because with more money in the pot they are more interested in participating in the hand.
In these cases I prefer to limp and see cheap flops with the low pairs and the suited conectors.
only limp/call strategy is pretty bad. In almost every situation you want to raise because your goal in poker is stealing the blinds. You can't win a pot preflop by limping. Plus you want to play bigger pots with your premium hands.