This should go without saying, but please, thank you, and basic respect for the person you're dealing with go a long way. A very nice woman at Geico found a way to cut my insurance premiums in half, and I've negotiated away countless toll fees for friends and family members. Hotel workers, hosts/waiters, and airline workers will also hook you up.

Customer service reps get so much shit from people, and if you're the nicest person they speak to that day they will help you.