Best way to whiten teeth non professionally?

OTC Products. OTC products may help whiten your teeth somewhat, but they will not give you the same results as professionally dispensed kits. The strength of the OTC gels are not as strong and do not penetrate your enamel as well. Surface stains and calculus should be removed first (by a dentist) before you attempt whitening.
Good habit. some strips may help. but avoid too much coffee, coke, smoking and brush teeth regularly after each meal.