Slice a lemon and squeeze the juice into a container. Dip your nails into the juice and let it soak into your nails for 10 minutes. Rub a lemon wedge on your nails if the stain lingers. Rinse thoroughly with water and dry your nails. Moisturize your nail bed with oil or cuticle cream.
Place your hand over a basin or shallow bowl and pour straight white vinegar on your nails. Let it sit there for a few minutes, then scrub with the soft toothbrush. Rinse your nails thoroughly with water, then moisturize.
Plop two denture (fizzy!) cleaning tablets into a small glass of water. Dunk your nails into the water for a few minutes, and let the fizzing action get to work at removing those stains. Scrub with a soft toothbrush, then rinse thoroughly. Moisturize hands and cuticles.
Buff the top layer of your nails with a soft nail buffer to rub off any stain that remains. Don't buff deeply or scrape your nails with a rough nail file. You don't want to remove the nail's layer, just the stain sitting on top.