I recommend

Showing the dead rat in the pool to the visitors center's director, aka Mark Eubank the Weather Guy.

Here are some things I think you should do if you go to Oahu:

• Stay on the North Shore. At least for half the trip. Rent a condo at Kuilima Estates at Turtle Bay, perhaps. Vrbo.com will get you there.
• Eat at the shrimp trucks in Kahuku. Giovanni's is our favorite. Get the scampi.
• Spend a day at the Polynesian Cultural Center. Do the luau and evening show, maybe the IMAX. You can hop on a quick tour of BYU-Hawaii and the LDS temple, or go there on your own another day. Very pretty.
• Sing, "Oh, I'm going to the Hukilau. Huki, huki, huki, huki, huki, Hukilau." And then go to the Hukilau Beach for a sort of Hawaiian Provo/Mesa experience, if you know what I mean. Lots of one-piece bathing suits and big Polynesian college boys wrestling on the beach. Maybe you don't know what I mean.
  
• Pick a beach, any beach. Don't settle for crowds. You can have a beach all to yourselves without much trying.
• If it's rainy, chase the sun on the west (leeward) coast. It's most likely to be sunny and you'll get a cultural experience. Otherwise, you'll likely not go to this area, and that's fine.
• Visit the beach at Turtle Bay. It's gated, but it's a public access beach, and they'll let you in for free. Snorkel here if you want.
• Stop in at Ted's Bakery for delicious lunch to-go. Coolest (yet painfully slow) sort-of dive in the heart of surferville. Get the legendary pie! It's cool, really.
  
• Go to Haleiwa lots and lots, mostly to eat: the greatest burgers ever at Kua Aina, shave ice at Matsumoto's (you'll know it from the line out the door; try it with ice cream or beans), most delicious Thai food at Haleiwa Eats, banana fritters and fried ice cream at Rosie's Cantina.
• Waimea Valley is a very beautiful and pleasant walk, and rewards you with a swimmable waterfall hole at the end. (Lost alert! THE waterfall! You know, the dead bodies, and briefcase, Kate and Sawyer?)
• Speaking of Lost, it's fun to look up filming locations and visit them on a drive.
  
• Skip the Dole Plantation unless you're really into the tourist traps. Or if you want to see how a pineapple grows, which is sort of cool. If you do go, get the pineapple whip ice cream inside. Skip the maze, for heaven's sake!
• Off the beaten path: stop in at Goodwill in Wahiawa for all your Hawaiian shirt and muumuu needs. THOUSANDS of them. Very cheap. Kind of a fun side trip when driving into town from the North Shore.
• Pearl Harbor and the Arizona memorial is worth it. It's a sacred experience. The only free thing you'll do, besides the beach.
• Really fantastically beautiful hike on the East coast, windward side. A place called Haaula --your guidebook will get you there. Sketchy at the trailhead, but persist! It is stunning. Plan on two hours or so.
• The Halona Blowhole is fun to stop at. We saw a ton of whales not far from shore here.
• Visit Chinatown. Eat at a restaurant where apparently the health code doesn't apply. Ups the authenticity factor, and the taste of the food.
• Hike Diamondhead, although be prepared for millions of gnats at the top.
• If you have a military ID, buy groceries (don't forget pineapples and souvenir chocolates) at Hickam Air Force base commissary. Your grocery bill will thank me, three times over.
• Hit the Aloha Stadium swap meet on Wednesdays, Saturdays, or Sundays. Avoid buying souvenirs elsewhere at least until you've been here.
• Go to church. I love to go to church on vacation to get a feel for the people.
• Buy unusual fruits at roadside stands.
  
• Really, just disregard this entire list and lie on the beach every day. Don't forget sunscreen and a good book.
  
• Have so much fun! (That means you, Carrie!)

Anyone want to add anything? Please do!