Tomorrow in class, I'll spend extra time going over problems 2, 4, and 8 (and will try to post further hints tonight). I think those are the trickier problems with the most subtlety involved. Several of the others just have one silly trick you might not have caught yet, and will probably not seem so bad once you know the trick.
Also: my view on homework is that if you don't learn something by doing it, everyone's time is wasted. Given that, don't feel bad if there are problems you're not getting right away. If you understood it all right off the bat, there would be nothing to learn.