I agree with the practice drawing. I read somewhere that one of the biggest issues many folks had with longarm quilting was 'where to go next'. I first drew squares, triangles, basic shapes found in quilts. Then I filled them in with whatever design I was practicing. This helped me figure out how not to get stuck in a corner, and if I did, how to get myself out.
I also started practicing on a piece of fabric, but then made some scrap quilts with actual blocks. You can also check your LQS to see if they have any 'cheater' cloth.