This is from the Greg LeMond book "The Complete Book of Bicycling" I did it and it made alot of difference in my stroke, speed and endurence.

" How to Fit Your Bicycle

If you're too low on the bike, your legs will be bunched up and you won't be able to use their full muscular force. In addition, you'll be straining the legs because they will have to work harder to achieve the same speed; you will tire out much more quickly. In addition, the strain from the muscles will act as a source of stress for all your connective tissue-ligaments, cartilage, and tendons.
If, on the other hand, you're riding too high, you will stretch out too much and you won't be able to achieve full power in the crucial down stroke of your pedaling motion. In addition, you'll be constantly overstretching the muscle and connective tissue of the legs-a ripe situation for muscle pulls and connective tissue injury.
(If all this sounds terribly serious, to put it in perspective you could probably hurt yourself much more easily by running in the wrong shoes, because running is much harder on the body than cycling.)
Finding the right position, in fact, should be quite easy. To measure your overall height, you begin with the same inseam measurement you used to determine your frame size. Next, take that number and multiply it by .883, This figure was developed by French coach Cyrille Guimard. It's the result of numerous tests and years of experience with professional riders. My inseam is 84.3 centimeters; multiplying it by .883, I get an overall height of 74.4 centimeters, or 29.3 inches. That is the overall distance, in a straight line, from the center of the bottom bracket to the top of the saddle. Remember, though, that what's meant by the top of the saddle is the cupped part where you actually sit, not the lip that rises to the back of the saddle.
To determine your overall height, adjust the seat post and saddle so that the total distance from the center of the bottom bracket axle to the top of the cupped part of the saddle is your overall height measurement. In my case, if I adjust my saddle correctly, that distance is 74.4 centimeters or 29.3 inches.
Remember that this overall height formula was determined with the standard Campagnolo racing pedals and standard, medium-thickness cycling shoes such as Brancale, or Sidi nylon mesh shoes.
You should always measure any distance in a line parallel with your seat tube. Since your crank set sticks out farther than your saddle you'll need to add two or three millimeters to your measurement when using the tape measure, or you'll get a shorter overall height measurement.