Avoid nail products that could cause an allergic reaction, like those with ingredients listed on the previous page. And don't trust nail hardeners: Brittle nails actually are already too hard, and nail hardeners produce allergic reactions in some people. You're better off moisturizing your nails.
Keep your cuticles: They're actually important for nail health, and trimming them excessively can leave you more prone to an infection. Cutting them may also lead to nail deformities. If a hangnail or excessive cuticle is bothering you, use scissors to cut cleanly and moderately.
Lay off the nail polish occasionally. It gives your nails a break, letting them breath and allowing you to look at the physical appearance of your nails and make sure there aren't any issues lurking underneath the polish. Moisturizing creams will be better able to do their work on an unvarnished nail.
You should also minimize the amount of nail polish remover you use, applying only as much as is necessary to remove the polish. As we said before, avoid removers containing harmful ingredients like formaldehyde, which dries out nails.
Finally, it's good to let your nails get some air, but keep an eye on how they're affected by the environment. Cold, dry air can lead to cracking.