Your Bike Fit
It’s important that you correctly fit your bike for both performance and health reasons.  Many people say they can fit you to your bike.  So how do you decide who to choose to do your fitting?  Some option are to go to a professional bike store and get fitted or where you purchased your bike or go to a professional bike fitter.
It's important to first understand the difference between bike sizing and a bike fit. If you're purchasing a new bike, remember that bike sizing is done to determine the correct bike frame size.  Bike fitting, on the other hand, alters the bike to fit the cyclist’s unique body architecture to maximize efficiency.  Bike sizing and bike fitting can - and sometimes should - go hand in hand.  Some cyclists purchase bikes only to learn the frame size is too tall or short which limits the range of adjustments that can be done during a fit.
A good bike fitter will use a multidimensional approach that looks at every aspect of the cyclist and their connection to their bike.  During a professional bike fit the athlete is asked a series of questions to determine their cycling goals, identify prior injuries, highlight discomfort felt when riding, and other pertinent questions. The athlete is watched pedaling, a measure of the athlete both off the bike and on the bike, and questions are asked about how they feel while he or she is riding.
One thing that differentiates pro bike fitters from your local bike shop is focus on the foot-pedal interface.  For example, an average cyclist completing a 100 mile ride ("a century") will have rotated the pedals 54,000 times* their legs/feet are clearly doing a lot of work.   Emphasis on the foot/pedal connection, fore/aft, side-to-side, tilt/angle, and rotation of the cleats is very important.
Check this out if you’re not feeling comfortable on your bike or are buying a new one.