What amount do you preflop raise?

As far as I can tell there are 3 schools of thought for open raising in NLH tourneys.

1) Every raise is the same in relation to the blinds. typically 2.5 - 3 x BB no matter what cards you hold and decide to raise with

2) Your raise is in relation to your cards. Big pairs = Big raise , weaker cards = smaller raise.

3) Mixing it up. Doing anything from limping to a big raise with no relation to your hand strength to keep your opponents off balance.

I typically use the first theory but have run into several successfull players using the third. The second seems to be a little to predictable and I like it when an opponent does this at the table as it provides me with more information. Any thoughts as to which way is better against different styles of players? Which do you typically use?