The flight in to Baltra was uneventful, but it was a bit strange to see that the runway traversed the entire length. There is a reasonable airport facility with clean restrooms and minimal food and drinks but it was comfortable. Upon arrival you'll be transported by bus to one of two docks where you'll board a Zodiac for transport to your boat/ship. If you have a bit of time before the buses depart, or before your flight back home, you'll have an opportunity to buy souvenirs in a small series of shacks set up behind the airport.
We found endemic wildlife even before we left Baltra. Frigate birds, Sally Lightfoot crabs, marine iguanas and even a few sea lions were visible from the dock area. Of course the temptation was to grab your camera and take a shot -- but I can tell you that these pictures will pale next to the opportunities you'll have on any of the islands you visit. On this topic, the one thing I noted as a professional nature photographer was that many people did not plan well for taking advantage of these photo ops. You won't need a professional camera or a telephoto lens (though I had two of each), but be sure to bring extra batteries, plenty of memory cards, and be sure to make certain you either have a waterproof camera or take caution to keep yours out of the seawater. Of the 90 or so passengers on our ship, at least 8 to 10 had their cameras fail either from dropping them on the rocks, getting them wet, or assuming that "water resistant" was the same as "waterproof". You don't want to ruin your trip by being without a camera, so think about taking a spare.
What you'll find is plenty of chances to see sea lions in harems, cows nursing babies, hundreds if not thousands of iguanas, and plenty of birds. What you won't find, unless you go in the rainy season, is much in the way of flowers. Most of the trees and bushes have adapted to the brine conditions and though green won't show much in the way of blossoms. If you are lucky you'll get a chance to snorkle with turtles and sea lions, both of which seemed content to swim close by. If you have a waterproof camera you may get some good underwater shots of these amazing creatures. But you don't need to take pictures to enjoy the surroundings, just keep your eyes open and listen to your guides who are very knowledgeable.
The largest island, Santa Cruz, is home to the Darwin research station, and is the only place you'll be able to observe the famed Galapagos tortoises up close. In the edges of the rain forest in its interior you will likely face the prospect of rain so take a rain jacket. You will also want a hat and/or sunscreen since you will be at or near the equator on all the islands. At the end of your days aboard ship keep your eyes peeled for some stunning sunsets. We also spotted dolphins, turtles, a couple of whales in the distance, and manta rays leaping from the water to rid themselves of parasites (something I'd never seen before) so not all the life is on the islands themselves.
In terms of physical requirements you should be in reasonably good shape to enjoy the trip because you are going to be on islands with little or nothing in terms of human improvement (meaning you won't find latrines!). Hiking is different on each island, ranging from soft sand to gravel paths to walking over lava fields and rocks. And of course it will be helpful if you can get on and off the Zodiac boats without flopping into the water and soaking your clothes. However, the average age of our ship's passengers was well over 50 and there were no children (probably due to the cost and the absence of phone coverage and iPads!). For footwear you can wear surf shoes or Teva sandals for most of your hikes, though you may want to carry tennis shoes or hiking shoes for some of the drier islands and longer treks. Depending on which tour company you travel with, you may seen two or three different sites each day with distinctly different weather conditions.
Before or after your trip to the Galapagos archipelago you may wish to extend your trip by visiting Peru and the Machu Picchu Mayan ruins. If you do, it's an easy flight to Lima Peru from Quito but then you'll likely stage in Cusco where the altitude is 12,000 feet. After a week at sea level we experienced mild altitude sickness, but the good news is your hotel will likely have oxygen bottles to help you cope, and the really good news is that the mountains of Machu Picchu are actually much lower altitude than in downtown Cusco. That side trip was a delightful add on and not terribly expensive considering you've already flown to South America. I would encourage you to use a good tour company or take a cruise ship to avoid having to plan all the transfers and transportation on your own, but I have friends who have been several times and navigated on their own on subsequent trips.