I would add one thing to caymaniac's sage advice:
When you travel, you are an ambassador.
Help raise the awareness in others of the fragility, beauty, and importance of these reefs.
My wife and I were fortunate enough to dive in the Virgin Islands, FLorida Keys, and Jamaica this summer. Although the Keys probably have a higher total number of divers, the reefs there were in the best shape -- because of the passion and concern that the dive shops and fishing industries have there, and because of the way they raise awareness with divers and snorkelers. Jamaica was, by far, the worst, and it was very depressing to see the vast amount of damage to the reefs in Negril. I found it easy to begin a conversation about the condition of the reefs with the other divers on the boat as well as the divemasters. Each of us can make a difference!
(Climbing down from my soap box, now)
Scuba Legs