Most of the time, not at all. The majority of my drawings aren't even inked, because the 'sketch' is clear enough as is. I don't enjoy having to redraw things, so I make each line as clear as I can when I put it down.
However, when I'm doing a weird perspective pose or just trying to force myself to finish a comic update, the paper can turn into a real madhouse. When I'm drawing in aggravation, I go crazy; sometimes I don't even touch the eraser until after the inks are done. 'Just get it down; if it takes 50 strokes to get the torso shaped right, so be it! You can get rid of the garbage after you finish!!'