before adjusting cleat position, is your saddle position correct?

http://www.sheldonbrown.com/saddles.html#height
http://www.peterwhitecycles.com/fitting.htm

start from there.


then when that's all good, for cleat alignment, as a general guideline:
the center of the pedal spindle should be on the ball of your foot and you position your cleats so that your feet will be parallel to each other. from there you do minor adjustments

knees that bow inwards, knock knees, would mean your cleats are too far inward, or your saddle is too low, or both. generally your feet will be closer at the toes than the heels so you will have to move your cleats inwards so that your feet get a wider stance.

http://www.caree.org/bike101cliplesspedals.htm
http://www.cptips.com/knee.htm