Understand its history. The slang language of Hawaii, or "Hawaiian Pidgin," evolved from the early interactions of the many peoples who immigrated to the islands; it contains elements of Japanese, Chinese, Portuguese, Filipino, Hawaiian and English. Today, it is used as a familiar lingo among the locals.
Learn some useful phrases. Gathering a list of common terms will allow you to incorporate Hawaiian Pidgin more easily into your vocabulary. Basic phrases to keep in mind include: "howzit" ("how are you?" or "how's it going?"); "lua" (bathroom); "brah" (universal form of addressing someone, similar to "dude"); "kane" (men); "wahine" (women); "ohana" (family); "ono" (delicious); "ainokea" ("I don't care"); "pau" (done, finished).
Slip your newly-acquired slang into conversation. When out and about in Hawaii, show the locals that you appreciate and respect their culture by using some pidgin terms. Make sure to pronounce them correctly but don't go too overboard with a false accent, lest people think you are mocking their speech.