Composition and content are vital for sky shots.
Sometimes the shape of the cloud formations you see can make a photo on its own. There are even websites dedicated to photos of unusually shaped clouds. There are no right and wrong answers, use your imagination. Here are some very effective examples from You Connect members.
As painted, © Lothar Nolting 2011, Canon EOS 1100D
Faroe Islands, © Frank de Groote 2011, Canon EOS 7D
Cranes heading south
, © Steffen Grönke 2011, Canon EOS 40D