You will need several leis, brightly colored flowers and tiki torches, that can be as simple or as elaborate as you would like. For added ambiance, use tropical fruit such as pineapples, coconuts, mangoes and papayas as your centerpiece. Use grass hula skirts as table skirts, and coconut shell candles scattered about. Throw in a Surf DVD for some cool surf vibes in the background.
Go to iTunes and download a mix of steel drum music, reggae by Bob Marley, and other mellow Hawaiian tunes.
Start the evening with a Polynesian pupu platter; Island-inspired faves like coconut shrimp and mini squares of pineapple pizza are great.
Whip-up a batch of Piña coladas, daiquiris (don't forget the umbrella toothpicks), and fruity cocktails with names like Blue Hawaiian and Wailin' Marley. If your graduate is under 21; then make it a virgin.
What luau would be complete without the Limbo Contest? The only thing you will need is a long stick, curtain rod, or broomstick. You can also have fun with a hula hooping contest or contest for the ugliest Hawaiian Shirt. You can also hire someone to give hula lessons during the party.