YOU'RE hitting 6-irons into greens when your buddies are hitting 7- and 9-irons from the same distance.
Simple: speed. Adding extra miles per hour to your swing is the only thing that's going to allow you to hit each of your irons farther. Most amateurs think of speed as something they generate from the top, but that's a recipe for almost every bad shot you can imagine. The secret is to maximize the fastest part of your swing, and that comes after you strike the ball. Copy the release positions here and you'll learn to accelerate through the ball and into your follow-through, making your impact faster and adding yards to your irons.
CENTERED HEAD It's important that your keep your head centered over the impact area. This allows you to make your swing as wide as possible on the target side of the ball (just like you should on your backswing). If your head moves in front of the ball, then you're limiting the radius of your through-swing and robbing your swing of crucial miles per hour of speed.
LEVEL AND STEP Swing into your release with level hips (or as close to level as possible) and steep shoulders. Notice how much lower my right shoulder is compared to my left that's evidence of my right shoulder working under my chin, not in front of it. This right-shoulder-under move allows you to move your club at a right angle to your spine, which is the fastest route possible.
RIGHT-HAND SLAP Notice how far the clubhead has traveled from impact to its position in the release, but how my hands have only moved a few inches. The difference between these two distances is what makes your release the fastest part of your swing. You can achieve this hidden speed by giving the ball a right-hand "slap" through impact, and continuing the slap in your release so that your right arm gets very long with the club as far away from your head as possible.