One of the key elements of my GMing style, I've realised, is that I tend to involve the players in the decision-making process rather a lot, so while I'm the final arbiter, I'm always open to suggestions on rulings and ideas on how to handle things. For instance, let's say I'm GMing a game where the rulebook doesn't include anything on calculating damage from falling and one of the PCs is falling off something from a 30 foot height. I'm just as likely to say to the players as a whole, "What do you reckon? How damaging would that be?" and let them have some input into the final decision as I am to just say, "You take 1d20 damage" off the top of my head.
I'm also likely to draw on the players' expertise in decision-making processes too. My gaming groups include veterinarians, firearms experts, people with PhDs in mathematics, and computer scientists. It would be almost perverse not to draw on their knowledge to make decisions and rulings that are realistic and sensible. (The firearms expert in particular always comes in handy; "John, would a 12.7mm round penetrate the brick wall Andy's character is hiding behind?" "Yes.")
Reading around forums and watching other GMs, I realise that this isn't really the norm, or at least I do it more than most. I can't really understand why. I take the view that we're all adults, and my players know I'm not God - it's not like I'm shattering any illusions by revealing I don't know something or I could do with knowledgeable input.
It also seems to me that sessions always run smoothly when it feels as if everybody is pulling in the same direction. My GMing decisions are generally as objective as I can make them and I try to create a neutral game world with rational consequences, but it doesn't hurt for players to feel as if they have some input into the process of refereeing - it gives things an atmosphere of consensus and collegiality rather than of paternalism.
Let's face it - I'm also pretty lazy, and the more I can farm out and outsource to the players, the better.