Every island has a north shore, but there is only one North Shore, on Oahu, known to surfers around the world. Within a few miles along the surprisingly rural Kamehameha Highway are four breaks that hold competitions on the world pro surfing tour: Haleiwa, Waimea Bay, Pipeline (pictured), and Sunset Beach. Waves with 10-foot faces are common, especially in the winter, and frequently the walls of foaming water reach 30-feet and higher.
Spectators are free to pull in and watch the world's best surfers for free. When the waves are right, they will come. Haleiwa town has plenty of parking at Haleiwa Ali'i Beach Park, but the break is a little far offshore for optimum viewing. Just down the road at Waimea Bay (yes, the one named in the Beach Boys' "Surfin' USA,") has a big parking lot, but it fills up fast when the big waves arrive. Spectators head for the mouth of the bay (you can park at a nearby church) to watch the show from a bluff.
A bike lane connects near by Pupukea (town) to Pipeline (at Ehukai Beach Park) and then Sunset Beach, which is only a couple miles. Beach cruiser bicycles are available for rent, cheap, making for a lazy way to check out the scene. Pipeline has sand that slopes down to a near-shore reef break, a natural grandstand for spectators. Tour buses pull off at Sunset Beach, since there is a big turnout. Sunset gets a lot of looky-loos, but it's not among the best places to watch.
For details on the best places to surf, and to watch the big boys and girls challenge the waves, check out Oahu Trailblazer. (All the Trailblazer guides list the best surfing in the Islands, as well as the best place to have a seat and behold.)