I’m still trying to work out this fineliner thing. Memadtwo (or one of them!) pointed out how you can just leave your “wrong” lines be, and draw on top of it with a “correct” drawing.. Maybe I ought to work with much more general lines to begin with – I think i tend to start off a little too detailed (draw and eye, then another eye) instead of drawing the overall shape first, and then gradually detailing it all at once. Anyhow, when you’ve drawn an eye, it’s hard to move it, without it all just becoming a mess of black ink that shines through any type of correction you might aspire to make. In the case of the prime minister above, I would have lowered his eyes a little bit and redone his mouth. I tried to fix the mouth a bit up with some white gouache, and even though it looks like it didn’t work, I assure you that he looked more dangerous before!
The best remedy when you get that feeling of a drawing starting to “go bad” is just to opt for expressionism and go a little wild.. People will think that the distorted features are made on purpose ! (didn’t you think that?)