If you want to stop biting your nails, then you must start visualizing yourself with strong, healthy nails, and how great they look. You should consider getting a manicure as you start off your nail biting-free days.
There's this fingernail polish that you can buy. It's very bitter so you'll be able to resist biting them and it also makes them grow. You can buy it at your local drug store or supermarket. I forgot the name of it though