Clothing/Shoes/Weather Gear: Well, what can I say. You are likely going to visit the most voluminous falls in the world, and you are looking for tips on what to pack? One thing that is certain is that you will in fact get wet. The spray from these falls alone is more like a torrential downpour in certain places. But on the other hand, it is extremely warm and muggy here when you are not getting rained on. So I would recommend that you bring a nice light weight rainjacket and rain pants if you really want to get in and enjoy the falls to the utmost. You can likely stay far enough away if you really had to, but what fun would that be?
Clothing/Shoes/Weather Gear: If you are on the Argentinian side, a raincoat is a must as the trails take you very close to the waterfalls. If you are there in the summer, getting wet might not be a big deal, but if you are there in the late fall, as we were, it can get quite chilly. Buy one in the giftshop, or bring your own if you don't want to get soaked!
Foz is a really hot place... I was there in autumn (well... it was supposed to be autumn!!!) and during the day the temperature was about 35 - 40 ºC (95 - 104 ºF) and it is pretty damp... Something like an open air sauna!!!
Foz es un lugar realmente caluroso... Estuve allí en otoño (bueno... se suponía que era otoño!!!) y durante el día la temperatura oscilaba entre 35 - 40 ºC, y es bastante húmedo... Algo así como un sauna al aire libre!!!!
Miscellaneous: Bring your ATM cards, but keep in mind they might not work at all banks. I had to best luck at the Banco do Brasil on Av. Brasil, but even there you have to look for the machine with the stickers displaying the ATM networks (Plus, Cirrus, Interlink, etc.).
It can get hot here in the summer (remember summer time is opposite than in the northern hemisphere), but it gets colder here in the winter than in many parts of Brazil.
Photo Equipment: Bring your camera equipment for photographing the falls. You will want a good zoom lens, a polarizing filter to make those rainbows sing and you may want to experiment with slowing the shutter speed down to give the moving water a smoothed out look.
Miscellaneous: Bring bug repellent for hiking through the national parks.