The bold paragraph sums it up.
http://www.fulltiltpoker.com/proLessons.php?lesson=20
Lesson: 20
Sizing Up Your Opening Bet
Chris Ferguson
August 1, 2005
I never get tired of saying it: If you're the first to enter the pot in a No-Limit Hold 'em game, never call. If you aren't prepared to raise, throw your hand away.
Why, you ask? Simple. By raising, you put pressure on the blinds and the other players at the table, making them consider just how strong their hands really are. Chances are that by raising, you'll force marginal hands to fold before you even see the flop, limiting the number of players you have to beat through the rest of the hand.
OK, with that out of the way, the next obvious question becomes: How much should I raise?
To that, I say; it depends. First off, you shouldn't allow the strength of your to hand affect the size of your raise. A tough poker game is like real estate. The three most important factors in deciding how much to raise are: Location, location, location.
You always want to make your opponents' decisions as difficult as possible. In choosing the size of your raise, you want to give the big blind a tough decision between calling or folding if the rest of the table folds around to him.
Raising from early position is to advertise a very strong hand - one that can beat the seven or more other players who still have to act. Since you are representing such strength, it doesn't take much of a raise to convince the big blind to fold. Also, since your hand is so strong, you actually don't mind a call from the big blind anyway. The real reason for a small raise is that you have so many players acting after you, any of whom might wake up with a monster and re-raise you.
When you raise in late position, you're representing a hand that can beat the two or three remaining hands. This gives you a lot more freedom to raise with marginal hands, but your raise must be bigger or the big blind can call too easily. Another reason to raise more from late position is that you're trying to put pressure on the big blind to fold, not call and, more importantly, you don't have as many remaining opponents who can re-raise you.
One of the most common mistakes in No-Limit Hold 'em is coming in for a raise that's too big. In early position, you want to keep your raises at about two times the big blind. With four to six players to act behind you when you're in middle position, raise to about two and a half big blinds, and raise to about three times the big blind from late position.
If you're representing a big hand by raising from early position, it stands to reason that you'll only get played with by huge hands. Why risk four, five or more bets to win only one and a half bets in the blinds when you're often going to be running into monsters along the way? If you're holding A-Q rather than A-A and a player comes over the top, you can lay it down without having risked much.
Some beginners raise more with their strongest hands to build a bigger pot or raise less with these monsters to get more action. Instead, I recommend that you play your starting hands the same way no matter what you have. With A-A or A-J, raise the same amount so you're not telegraphing the strength of your hand to watchful opponents. An exception would be if you know your opponents aren't paying attention and you feel sure that you can manipulate them.
These numbers need to be modified if there are antes. You should generally add about half the total antes to any raise. Your early position raise should be two big blinds plus half the total antes, and three big blinds plus half the antes for your late-position raises.
There are many loose live games these days. If you find yourself in one of these games and you can't steal the blinds with a normal raise, tighten up your starting requirements slightly and make larger raises. If this raise still can't take the blinds, don't tighten up anymore, but choose to raise an amount that you expect to get called once or twice behind you. Since your opponents are playing too loose, take advantage of it by building bigger pots when you think you're getting the best of it.
The last exception is when you're short-stacked. If making your typical raise means putting over a quarter of your stack in the pot, just go ahead and move all in instead. Betting a quarter of your stack before the flop commits you to calling just about any re-raise or, at the very least, it gives you a very tough decision. Moving all in here instead of raising less forces the tough decision on your opponents and eliminates one of your tough calling decisions. All of which brings us back to my first principle: Avoid being the one to just call.