Renting a car and exploring at your own pace is the best way to see any of the main islands in Hawai'i. The aloha spirit isn't the polished clockwork of a German village. Behind the tourist facade, many countryside residences are rustic and a little bit weatherbeaten, much like the islands' ancient volcanoes themselves. This is a place where people actually live and pay taxes, not just play in a Disneyfied paradise. And, scheduled excursions are the antithesis of island life. Still, a little planning can maximize your adventure and comfort.
Honolulu on O'ahu is sprawling, and traffic can be congested. There are a lot of one-way streets, so a GPS or your mobile phone map app will be invaluable. I'll swear the freeway lanes are narrower than I'm used to on the mainland. I was constantly running over the lane-side (warning) rumble strips, which at least kept my wife alert. One good thing, when you leave the city to explore in the morning and return in the afternoon, you will be going against the flow of rush hour traffic.
Maybe this is your first full day in Hawai'i, and you find yourself bright-eyed and ready to go in the darkness of 5:00 am? This was our condition on our first morning. An early morning climb in the crater of Diamond Head was the perfect way to offset the effects of jet lag.