The tour company picks you up at your hotel (2:30am for us) and others in their van, takes you to their HQ to watch a bike riding safety video and to get the bikes, then drives you in the dark the 1-2 hour ride to the summit of Haleakala. There you don wind/rain suits (which, even if you've bundled up, is very helpful in keeping you warm in the 30-degree dark), drink some coffee, eat a pastry, and wait for the sunrise.
As the sun starts to brighten the distant horizon, the picture-taking commences, until the full fire-ball appears and seems to light-up the entire sky. Only at that time can you see the outlines of the large moon-like crater that last erupted over 200 years ago. Some 40+ miles in the distance you can see the twin peaks of Mauna Kea & Mauna Loa on the Big Island in a sea of white clouds.
The bike ride begins shortly thereafter -- all downhill -- on the winding road out of the national park, past the pastures and old ranches, down the side of the dormant volcano. You eventually make your way to the small cowboy town of Makawao, which is where, as our tour-guide commented, many people who want to get lost from civilization end up.
After shedding the wind/rain suits, gulping down a hot breakfast of eggs or pancakes (radioed ahead so it's basically ready when you arrive) and strolling around the town a bit, you're back on the bike to ride another few miles (with a little more pedaling, but not much) past sugar cane fields to Maui's north shore at the town of Paia, home to a number of quaint stores. After some more pictures at the beach, its back in the van for the journey home, arriving between noon and 1pm, and ready for a well-deserved nap.