To treat and prevent diaper rash, it is important to change the diaper as soon as it is soiled, gently clean the skin with warm water, use alcohol-free disposable wipes, apply a non-scented zinc oxide or petroleum jelly ointment, avoid talcum powder, use superabsorbent diapers, let the baby's skin air out whenever possible, make sure the diaper fits properly, and consult a doctor if the rash lasts more than 4 days or if there are other concerning symptoms.