Like Rich says it really depends on the photo, there are no hard and fast rules as to what makes a good composition - but there are some useful tricks you can use to make it better.

For me a good image should have depth. Something to draw your eye in and lead it to the focal point. It might be a road or track or a fence even leading into the frame, or a rock or plant in the foreground. It usually, but not always again it will depend on the actual shot, works best with 'lines'  running from lower left to upper right of the frame. Adding interest to the foreground can often turn a good shot into a great one.

It really is very subjective. There are some good tips on composition here...

www.dcmag.co.uk/Vital_Skills.aN_XJz4.html

• Andy

www.natural-photo.co.uk

"Dodging and burning are steps to take care of mistakes God made in establishing tonal relationships.  ~Ansel Adams"