This is going to sound like a rant, but I think it bears repeating:

A key piece of advice is often posted on here, in guide books, and on other websites: Greet the locals you talk to before you make your request/order/demand, etc. Take the time to slow down when you get to the counter or cashier and offer a genuine, "Good afternoon. How are you?" Remember they're there to help you, but we are guests in their home. And when something isn't the way you liked it perfectly, try to roll with it. I saw a couple saunter up to the Hibiscus Bar in the airport and the lady didn't greet the bartender and then got kind of "diva-ish" about her drink order. No wonder why she didn't get good service.

Exercise humility - place yourself, in your mind, a little lower than your hosts and treat the islanders with such respect. It'll go further than you think.

Seeing the behavior of mainland tourists over the last week was painful.