• Comfortable Shoes - much of the state's outdoor pursuits involves lots of walking and hiking. At the very minimum, comfortable walking shoes are a must, but hiking boots are probably better especially if you're hiking on more primitive walks and trails. In fact, you'll want shoes that can better grip wet surfaces because of the humidity that tends to keep trails and rocks slippery.
• Hat - don't take for granted the dangers of UV radiation. A hat will at least keep your scalp from getting severely burned (especially considering how easy it is to get sunburned in a tropical environment). If you're wearing a broad-rimmed hiking hat, it could also help protect your neck, ears, and face.
• Sunscreen - again, given the sun's harmful UV rays, it's a good idea to protect other exposed parts of your skin from sunburn.
• Sunglasses - prevents cataracts or other harmful effects of prolonged exposure to the sun's ultraviolet rays on your eyes
• Bug Repellant - this can be controversial because the chemicals contained in these things can be harmful to the environment. However, getting eaten alive by mosquitos is not desirable either (especially if there's always that potential of getting some mosquito-born disease). In any case, the most effective repellants contain DEET, but they're smelly and toxic if used excessively. The better way to go environmentally, though not necessarily a comfortable one, is to cover your skin with long sleeves and pants.
• Layered Clothing - you wouldn't think of this in a place like Hawaii, but believe it or not, there are some places where the temperature can dip towards freezing. Such places are basically on the island interior such as the summit of Haleakala.
• Rain Coat - this will keep you and your equipment dry for the most part (with a rain poncho covering the pack in addition to the body). It rains a lot on the windward sides of the islands so this will at least keep you sane under such conditions (not to mention prevent your camera or other valuable electronics from getting waterlogged).

Some other things worth bringing to enhance your experience include...

• Water Shoes - this is actually more of a corollary of the above recommendation on comfortable shoes. That's because many hikes and walks involve walking in water - especially if you're crossing an unbridged stream/river. Ever since we've purchased Keens, we tend to exclusively hike in these shoes. We've noticed others prefer Tabis for amphibious conditions.
• Hiking Sticks/Trekking Poles - this is useful for longer and more involved hiking excursions. They provide you at 1 or 2 extra "legs" to maintain your balance on stream crossings or alleviate shock to your knees if you're carrying a pack
• Lots of Memory or Film or Portable Hard Drive - the first and third items are for digital photographers. In any case, you'll be taking heaps of photos and you'll want to make sure you can bring all your photos home

Perhaps a greater nuissance is theft and break-ins, especially at trailheads or car parks out in nature. We've seen numerous places with broken glass undoubtedly caused by thugs who managed to smash in a car window. To counteract this, pay attention to your surroundings where you're parking your car and leave nothing valuable in the car as you're out and about away from the car.

Finally, nature is inherently dangerous and unforgiving. But in order to enjoy Hawaii's true paradise, that means going out into nature and being cognizant of these dangers. Below is a list of things you need to be aware of to stay safe in the outdoors...