The basics of Composition are simple...
If you took the shot stood up you should have squatted; if you squatted you should have laid on the floor; if laid (well done) perhaps you should have stood up
NEVER put the subject in the middle - unless it works, in which case it's brill
Use the Rule of 3rds all the time - except where it's better not to
Under/over-exposure is never a good thing - unless appropriate
Apply plenty of contrast/saturation unless it's best not to
Always use the 'right' aperture setting for max/min depth of field
Always use a shutter speed fast enough to stop the action dead, or blur it enormously depending on what you're after
Wide-angle shots are best, unless a telephoto would have been better (or vice versa)
Always set the right white-balance - apart from when you're warming/cooling the image
ISO is easy - set it to something appropriate to all of the above
If in doubt - hand your camera to the nearest kid and ask them to take the shot - you know it makes sense?
Hope that helped?