The Kalalau Trail is an 11 mile hiking route along the Na Pali Coast in Kaua'i starting at Ke'e Beach and ends at Kalalau Beach. Most people day hike to Hanakapai'ai and onto the waterfall in the Hanakapai'ai valley - this is 2 miles.
Camping at Kalalu beach and and Hanakoa requires a permit from the Hawaii DLNR. These permits sell out fast so it is advisable to purchase them way in advance.
You will encounter slippery rocks, numerous stream crossings so proper footwear (like hiking books or trail running shoes) is advisable. Some people like using flip flops or aqua shoes for stream crossings. As the case with any hiking in Hawaii bring a lot of water, bug spray, and sun protection. There are some parts of the Kalalau Trail that are exposed and it can get windy.
This is a very strenuous hiking trail that has over 5000 feet of elevation change so conditioning is a factor especially if carrying a backpack. For a moderately experienced backpacker with a 25lb pack it will probably take you 6-8 hours. A light backpack is very useful considering the elevation, technical terrain, and stream crossings and trekking poles are very useful for the elevation as well as for stream crossings.
Rain shelter is advised but it is generally pretty warm so you might find that bringing sleeping bags might be unnecessary. Some backpackers opt for just a rain fly and bug net. People often like to bring a light blanket and/or sheet in lieu of a sleeping bag. Water needs to be treated for leptospirosis which most filters are not equipped for so you will want to use chemical treatment. At the Kalalau beach there is a waterfall and a stream to refill your water and you might be able to pick some fruit like bananas and guava. There are numerous composting toilets at both campsites but no trash service so please pack out any garbage.
There are numerous opportunities for day hiking once you are in the Kalalau Valley. There are nice swimming holes and vistas to explore. The trail system is not well marked so take note of your surroundings.
Hitchhike, taxi, or take public transportation to the trailhead. If driving, it is advisable not to park at the trail head as car breakins are frequent. One can park 1 mile from the trailhead at Ha'ena State Park which is well lit and busy with car campers.
The Kalalu Trail is in general very safe but be respectful of other hikers and residents. It is a sacred place to the Hawaiians so it is important to respect this beautiful and special place. As with most strenuous hikes/backpacking trips be aware of heat exhaustion and dehydration.
Kalalau Trail - Very useful site with maps, further information about the trail
Trip Report - Trip report describing a hikers experience backpacking the Kalalau Trail over 3 days and 2 nights