The Harry Higley books on coverying are useful. The key to smooth covering for me was to use the technique of initially tacking down one spot, then pulling tension on the covering and tacking it on the opposite side. Keep pulling and tacking around the perimeter of your wing, fuse, etc. so that it is nice and taught, then just seal it all to the rest of the surface.

One tip to hide seams is to cover the bottom first, and then the top. When you do the top, allow enough margin to wrap cleanly around the bottom and no one sees the seam!