This is definately a must do! Take my advice start out in the morning and when your on the road to Hana don't turn around and go back the same way, continue going in one direction only! With all the stopping and hiking or even picture taking you won't be back until dark! At least we weren't!
We started out on Route 36 or 360 (same road) up by the airport by Paia. It's a road that travels along the coastline. From Paia to Hana is only 52 miles, but these miles pass through a variety of Maui's rain forests, winding through 617 hairpin turns and crossing 56 one lane bridges!
There are many places to stop along the way to go hiking or to swim under a waterfall so bring your camera and alot of film!
One place to stop is only about 11 miles past Paia, but you have to do some hiking. It's called "Twin Falls." It's the north shore's most popular waterfall at about 60 foot tall. The mile marker goes to number 16 but then it starts back at 0 so if your going by them pass #16 and go to #2 mile marker. If you're just going by miles it's around 18 mile mark. You'll probably see a few cars parked there. Follow the trail and it will take you to the waterfall and lots of scenery.
Pack a lunch and tank up your car in Paia, I don't remember seeing any gas stations along the way. They have a few places to eat in Hana, but we packed a lunch and ate at the seven sacred pools which is about 40 miles past Hana.
Hana isn't the attraction the entire road is, around every turn is a kodak moment! Remember when you cross one of the 56 one lane bridges slow down or stop and look for a waterfall, there's a good chance you'll find one!
As I said before don't turn around to go back to your hotel, It's faster if you just keep on going one direction! The road number change but you'll never turn off. Take Rt 36 or 360 then it turns into 31 than 37 and that will take you back towards the airport. Get a local map to get you back to your hotel a little easier.
Watch out for cows crossing the road past the seven pools, we had a few who wanted to take a rest in the middle of the road! If you go off road just be careful (as my husband will tell you) the lava can get very sharp on tires and puncture them! What a place to get a flat tire in the middle of no where!