Read that little page that knight linked you to. Also, think to yourself on how much bacteria that you are chewing when you do bite your nails. You should use a nailclippers if you do want to shorten your nails instead of biting them.
plus you have to cut your nails if you dont want to look like this:
It'll take years to get nails that long and you have to be extra cautious so you don't break one - so it's highly unlikely that nails would get that long...
My friend bought this nail polish. It is clear and you can't even tell it is there once it drys. It tastes very bitter so when you bite your nails you taste it and stop. It is used just for this problem. It worked for him really well.
I used to bite my nails when I was young but I eventually stopped the habit. My brother on the other hand still can't stop biting his nails. Even with a product that's supposed to stop nail biting, he still does it.
I used to bite my nails. I never really had a problem with it, I didn't want to stop and that was really all there was to it, but then I started rock climbing and stubby fingernails hurt, so I just stopped. I don't really know any specific way, I just told myself I wouldn't do it anymore.