[Shasown]

Either get them whitened professionally, get veneers, have them removed and replaced with pearly false ones. Use salt and sodium bicarb once a day when brushing normal toothpaste after all meals and sugar or acid containing drinks. Try to eat a balanced diet, drink more milk. Avoid certain types of drugs, some steroids darken the teeth from within.

Brush them with domestos, full strength bleach. It smarts a bit that one but makes them sparkling.(joking on the domestos by the way)