[Espy]

Before I read through everything else: SAI is, in my opinion, one of the easiest programs to get clean lines in. You always want to use multiple layers, especially if you're starting out, and make a pose skeleton first, then an outline, then the actual lines. (Least, that's what I do.)

To add to Gall's point: Drawing as you go really isn't a good idea unless you're really, reaaaally well-versed in your own style. Even I can't "draw as I go".