Start by soaking your finger nails or toe nails for a few minutes in warm soapy water to soften them. Scrub your nails gently with a soft-bristled nail brush to remove any dirt. Make a paste using 2 1/2 tablespoons of baking soda with some water. Spread paste on and under your nail and leave it on for about 3 minutes. Rinse with warm water. Pat dry. Repeat about once a week for optimal results.