Be aware that it is a very windy road & one lane bridges so it does take a lot of time to get there. If you do want to drive it yourself there is a great app called Shaka Guides, if will give you the best information & stories about the destination. It can be downloaded from the App Store for only $12.99.
If you’re not a confidant driver then it is best to book a tour. There are lots of options from private guided jeep tours, smaller & larger group tours.
If you’re staying in the north area of Maui it is best to leave as early as possible as it is a long day & you want to make sure you see as much as you can.
It is a wet area so be prepared for rain. Some of the waterfalls require you to walk to them whereas others are right off the highway. Make sure you have good walking shoes & a jacket.