DON'T buff weak nails.
DO increase blood flow in your nails by rubbing them together after you've oiled them.
DON'T use harsh, chemical nail-polish removers.
DO massage organic oil into your nails every night, like almond or neem oil.
DON'T forget your dose of protein: just like hair and skin, your nails are nourished by protein. So eat lots of meat, fish, legumes or tofu. If you're a vegetarian, make sure you're getting enough iron, and consider taking a daily iron supplement.
DO eats lots of foods rich in healthy oils such as salmon and mackerel, or nuts and seeds. Ground flaxseed is particularly good for your nails.