[Maverick]

that's a good start ^^
the only clouds I have ever draw are on my wild horse piece and they are pretty regular and simple, not so proud of them, so I don't have many clues, but you can use a white clean eraser for shaping the places were the cloud is shiny and white, those "pencil shaped" erasers are useful... but since I don't have one I use a common brick shaped white eraser, when It gets too round and worn I cut it with a knife so I can get a good edge for "draw" with it.
Using a clean tissue for smudge (sp?) the shading making it look more uniform might help, I usually smudge the sky since I can't shade in a really uniform way.
Use clouds pics for reference and experiment a lot XD