This is from an article that Phil Gordon wrote. It seems to make a lot of sense and is based on position,
"My pre-flop strategy is this - its raise or its fold, there's no in between. I'm not injured - I don't have a sprained ankle or a broken leg - so why would I limp? There's nothing wrong with seeing flops, but why let your opponents get in cheap with an inferior hand?
I like to size my pre-flop raises based on my position. A lot of inexperienced players raise based on the strength of their hands, but good players will pick up on this play before too long. If you always raise four times the big blind with pocket Aces, Kings, and Queens, but only three times with everything else, skilled opponents will notice these patterns and exploit them later on.
If, on the other hand, you always raise a predetermined amount based on your position, your holdings will be much better disguised. By adopting this strategy, it doesn't matter if you're holding pocket Aces or 7-8 off-suit (which is the kind of junk I highly recommend you don't play), your opponents will have a much harder time putting you on a hand after the flop. Cards aside, here's how I like to play before the flop:
- From early position - including the blinds - raise two-and-a-half times the big blind. You are more susceptible to a re-raise from this position, so it's best not to risk too many chips. Still, this raise lets everyone know that you mean business.
- From middle position, raise three times the big blind. Hopefully a couple of people will already have folded to you, so there's less chance of being re-raised. Hence, you can afford to make a stronger push and possibly steal the blinds.
- From middle/late position, raise three-and-a-half times the big blind. You really want to encourage those last couple of players to fold so you can go heads up with the blinds or just steal them outright.
- From the button, raise four times the big blind. You either want to steal the blinds or make it really expensive for them to re-raise you."