I recently explored Iguazu Falls, crossing it off my travel bucket list.
Here are some snapshots and key advice for your visit:

A glimpse of Salto San Martin from the Lower Circuit Trail

Viewpoint at Garganta del Diablo, also known as The Devil's Throat

Water splashing against rocks from the Upper Circuit Trail

Scenic view from the Upper Circuit Trail

Beautiful rainbow view from the Lower Circuit Trail

Alfred enjoying the view at Garganta del Diablo
Essential Tips for Iguazu Falls in Argentina
Embrace the early start. The park opens at 8 a.m. daily. Catch the 7:15 a.m. bus (costing $100 pesos round trip) from Puerto Iguazu to be among the first entrants. Begin with the Upper Circuit Trail for quieter exploration, then tackle the Lower Circuit Trail.
Get your ticket validated. You can enjoy a 50% discount on a second-day visit, but don't forget to have your ticket stamped before leaving the park. The entry fee for Iguazu Falls (Parque Nacional Iguazu) is currently set at 240 pesos as of March 2015.
Bring your own snacks. Dining options within the park can be pricey. Instead, consider picking up a ready-made sandwich for a few dollars at a bakery in Puerto Iguazu. The top bakery is located on Avenue Guarani near the intersection with Cordoba.
Stay cool and protected. Pack sunscreen, extra water, and an umbrella to shield yourself from the sun.
Don't forget your passport. There's a bus from Puerto Iguazu bus terminal to the Brazilian side of the park. If water levels are high, the mist may obscure your view. American visitors don't require a visa for a day trip.