If you plan on spending time hiking or exploring the outdoors, you'll need--as a minimum--a good pair of hiking boots, two change of socks, a compass and map. These will help you keep your feet in top condition and ensure you stay on the right road. A GPS may be a good idea if you're going somewhere not marked on local maps. A flashlight with extra batteries, waterproof matches, water purification tablets and sunscreens are also must-haves. Finally, bring DEET bug repellent, no matter the season. You'll also need a first-aid kit that includes pain killers, anti-itching cream, an antibiotic ointment and extra doses of any prescription medication you take. If you have severe allergies, you may want to bring a filled epinephrine syringe.
Pack light. You probably need a lot less than you think you need, so prepare a few outfits and then review them again and leave something behind. Even if you're traveling in summer, bring a light sweater. A poncho or an umbrella are a must if you plan on spending time outdoors. Clothing made of breathable materials are essential for hiking and backpacking, as are shorts or waterproof long pants, depending on where you're heading. Dressing in layers is always better, so bring several items that you can put on or take off depending on the changes in weather.
Accessories and Toiletries
If you're staying at a hotel, you will get shampoo, soap and other basic toiletries for free, so it makes little sense to cart them around with you. If you're camping or spending your time in the wilderness, buy organic products that are safe to use near water and won't contaminate the environment. Don't bring perfumes to use outdoors (it can attract certain animals) but do carry deodorant (non-spray is better). Toothbrush, toothpaste and a comb are a must for the outdoors and are sometimes not provided at simple hotels, so bring them with you. A book, a fully-charged iPod or a journal and pen can help pass the time during your travels or can be a nice way to relax before bedtime.