When out in wild country, the gear you have along is all you have to rely on. Until you get back to the comfort and safety of your home, it is up to you and whatever equipment you bring along to make your hike comfortable and safe. Failing to bring along the right stuff may mean a miserable experience or worse. That's why it's essential to bring reliable gear such as Merell and Patagonia sportswear.
You will generally consider clothing items based on the expected weather and demands of the particular hike location. For example rain or snow would require different gear than a desert environment.
The list below is not intended as some kinds of universal truth, if you disagree with something do different! However, if you haven't been to many trips like this before and don't know exactly what to bring, follow it as closely as you can and you will have everything you need:
1. Hiking boots or shoes, better with ankle support when hiking in a rocky mountain, or more comfortable styles like sneakers on paved rail trail. Water proofing boots or shoes is highly recommended for rainy weather (or snow or slush).
2. Hat that can provide cooling in the summer, warmth in the snow, and protection from sun.
3. Two shoulder backpack; big enough for all the stuff. Make sure that it fits comfortably.
4. Hiking Socks (thick ones): preferably of wool, synthetic materials ok, NOT cotton.
5. Pocket knife, possibly with a tin opener and a saw.
6. Flashlight plus spare batteries and bulb
7. First aid kit and private medicines if any.
8. Water bottle plus water if needed
9. Food: preferably with a low water content to keep the weight down (if water is readily available on the spot)
10. Rain Gear: jacket + trousers, they should be waterproof any tough enough to withstand sustained use.
11. Sunscreen, sun glasses, walking sticks, camera, extra shirts if needed.
12. Any other equipment or accessory that makes your journey more comfortable and easy.