Hana is found on the remote southeast corner of the island. The most popular way to get there from the more populated side of the island is by driving the famed "Hana Highway." It's only 52 miles long, but it'll take you close to 3 hours without stopping due to the numerous hairpin curves, one lane bridges, and people stopping to admire the incredible scenery. On your way here are a few great places to stop.
Twin Falls: Along the route. It's a great spot to pull over, hike the short trail, and go for a swim. It's one of the most famous of the many swimming holes along the Hana Highway.
Wai'anapanapa State Park: The main draw here is the volcanic black rock beach. Please realize that this isn't sand, but tiny volcanic pebbles. It's rough but fun to walk around on. There is also a small cave that opens up into the ocean to check out. This isn't a great beach for relaxing or swimming honestly, as the winds channel some pretty serious waves into the coast. It picked me up and slammed me on the rocks as I was trying to wade onto shore.
After your drive, you'll arrive at the sleepy village of Hana. Since this is usually just a passing point for tourists, you get a glimpse of what a small native Hawaiian village unpolluted by mass tourism and beach hotels is like. Because it's on the opposite side of the giant Haleakala volcano, it is completely isolated from the rest of Maui. The mountain even blocks radio signals, meaning you'll only catch sounds and news from the big Island to the south. One scenic spot to check out in Hana is the secret red sand (Kaihalulu) beach. The red sand are the remnants of an ancient cinder cone of red lava.
If you have the time and patience, driving onward from Hana around the southern part of the island you can find the Palapala Ho'omau church and cemetary tucked away down a inconspicuous side road. This beautiful little cemetary overlooks the Pacific, and is the final resting place of Charles Lindbergh, the famous aviator, who retired to Hana and spent his final years there. We literally spent a half hour driving down dirt road after dirt road hoping to find the cemetary, so patience is required. Just as we were about to give up, we found it. It was definitely worth the extra effort.
It's not an easy or inexpensive trip, but the trip to Hana, Maui is definitely worth it if you like traveling off the beaten path.