Trekking is a very tedious task for your feet. They not only have to walk on rugged and traitorous terrain all day long, they have to do it with you and your heavy backpack on them. So to make your feet a little happier and by extension you as well, here is a short list to help you keep your feet dry and capable in your treks:

Hiking Shoes: This is your first and foremost important thing to worry about when planning a hiking trip. The difference between good hiking shoes and poor ones could easily be the difference between a great trip and a leg/back/knee fiasco. All your equipment and the rough terrain are creating enormous amount of pressure on your feet and without the proper support sprained ankles sore feet, and a bad back are just a matter of time. Get yourself good hiking shoes, preferably water resistant – this is not the place to be cheap.
A good tip for trekkers with new shoes: take a few hikes before you go on long treks. Let the foot and the shoe get used to one another. No matter how good your shoe is, it needs to get used to your leg and vice versa, don't skip this part and you can avoid that "new shoe" sores you sometimes get during your first few long treks.

Sports Sandals: So useful it's simply a must have. Great for hikes, casual walks, can be used as a substitute flip flop and is basically the only other foot accessory you really need.

Flip flops: comfortable and handy, but takes up room in your already crowded pack. If you have sandals and not much room, just leave them at home. Besides, since this is usually not a very expensive product, if you must you can always get a pair during your trip.

Sneakers/Formal Shoes: Unless you have a really good reason to take them ("My sister is getting married on the top of the Kilimanjaro") – leave them at home. Your going on a trip, not a formal dance.

Waterproofing Wax: Guards your shoe and keeps it from getting wet. Not too expensive and it's worth it.

Orthopedic foot support: Not only for those with problems. The more support your foot has, the better. Can help lower the pressure and give you better posture.
Tip: Should you decide to get additional foot support, do it before you get your shoes and try your new shoes with the support surface inside the shoe to insure maximum comfort while walking.

Socks: Usually regular socks are ok, but if you fear your feet will get cold or tire you can also get some hiking socks. Nice to have, but if you don't want to spend more than you already have, don't feel bad about not getting the best socks in the world, just make sure they have no holes… :)___________________________________________________________________