Nail biting usually derives from stress. It's a coping mechanism that doesn't really work, even though our mind thinks it does.
Try to keep your mind and hands occupied when you feel the urge to start nail biting. Yoga, knitting, crocheting, exercising, cooking, puzzles, video games - anything fun!
Firstly, I always try to keep on nail polish. I'm always trying new styles of nail art, as well as new colors! It prevents me from chewing away at my nails. Why ruin that hard work?
Another option is to put on anti-bite polish. Just be careful about using it, because the taste gets on everything usually. Even in your food, if you cook barehanded.
Additionally, this is one of my favorite options. Chewing gum, you ask? Well, chewing gum or sucking candy keeps your mouth occupied, so your hands won't have the opportunity to be chewed on!
Don't get upset at yourself if you catch yourself nail biting. It's a habit that many people have. When you catch yourself nail biting, redirect your attention else where.
I hope you've found this helpful. If you have any questions or requests, feel free to ask! :)