Trying to create a realistic sky

Currently, I’m attempting to create a sky for my BWC entry. So for, it isn’t much, consisting of only a sphere with a blend and cloud texture. What do you do to create quality skys for your renders?

http://blenderartists.org/forum/showthread.php?t=24038

Or you could make volumetric clouds

The world backdrop renders fine for me but it has terrible resolution. How can I sharpen it up?