Best way to show respect to locals while visiting in Hawaii?

Be considerate. Before doing something uncommon, inquire about its acceptability.

It is perfectly acceptable for a haole ("haul lee") to say "aloha" (hello/goodbye) and "mahalo" (thanks). But English works fine too.

call them howlees and say that the states are much nicer then the dumps in pineappleville

Be friendly

The same way you 'show respect' any citizen in the country. Don't be a dick.

Be considerate of the people around you. Say excuse me and thank you. You know, general politeness. At least I hope you know how to be polite.

Hawaiian people are extremely violent and hostile. Be very careful. You are entering very dangerous and unpredictable territory. Gangs roam the islands and there are pirates and robbers everywhere. Don't look at any one the wrong way. Good luck! You are gonna need it!

Be nice to everybody are good words to live by. In Hawaii you will find just about two kinds of Polynesian people. I hate to say "two kinds" but it's pretty black and white. Those who like you will be loving and friendly and helpful like you never saw before. That will be most people. The others are of a state of mind that the white man stole the islands and overran the old ways with tourism. Those are in the minority and there's really not much you can do about them.

Learn to speak and use the Hawaiian Language.

Try just being polite. You are a Visitor a guest to some other place. Behave like one.