I bite my nails quite severely. Sometimes until they bleed - not all the time, but sometimes.
I've tried that bitter tasting nail varnish, normal nail polish, buying a manicure set and I've tried wearing gloves. Wearing gloves did work when I worked all day every day for 8 days at Sainsbury's before xmas. Now I work there 20 hours a week and between those hours I'm at Uni and it's SO BORING I bite my nails constantly.
Anyways, every time I go to my nans I use her clippers and I don't bite my nails as much, if not at all. So off I went to M&S and got some Autograph nail clippers. I can't remember how much they were and they've broken now (the spring has come off), but they've kept my nails in better condition than they were.
I still bite my nails, but there's less random bits of skin or nail that I can chew on. I know it sounds crude, but that's what I pick and bite at.
These are what mine look like. I find them easier to maneover them around my cuticles. Normal flat bladed clippers are good , but I prefer them to cut my toenails rather than my fingernails. My mum doesn't bit her nails, but picks the skin around the nail and she finds it quite handy to clip the dry skin off instead of peeling it away.
If you bite your nails, you'd benefit from investing in some of these. Don't forget your nail file as well though. Filing you nails is so nice! No nicks or bits of nail that will tempt you to have a good nibble.