When traveling oversees or in the USA, a good practice is to hand everyone who provides you with a service some cash. Giving everyone a generous gratuity or simply a donation is the thing you can do for locals that will make them happiest and their lives better. Tipping is against the rules where you are staying? Do it anyway. Hand money to every native around you when you visit their hometown, and feel no guilt about your sojourn whatsoever since they will all be glad that you came. If you can't afford to do that, stay home.