This article is the first in a series of five detailing each day of the W-Circuit trek in Torres del Paine National Park. The trek was completed starting with the Glacier Grey leg and going west-to-east, though it can be completed in the opposite direction as well.
The first step in your Torres del Paine trek is actually getting to the park. There are several bus companies that run from Puerto Natales to Torres del Paine, all of them will leave in two waves at 7:00 AM and 11:30 AM. The bus ride takes 2 hours so you should catch the 7:00 AM bus to give yourself enough time to hike on your first day. Bus tickets should be bought at least the day before. You can purchase tickets at the bus station in Puerto Natales or at Erratic Rock's equipment rental store (I would highly recommend their daily talk on Torres del Paine treks at 3PM).
The park entry fee is $21,000 Chilean Pesos and must be paid in cash. You're officially required to have already made reservations for your stay in the park at campgrounds or refugios to gain access to the park, in practice they were not actually checking people's reservations. This could change at any time and it is up to you if you want to risk it but it seemed unlikely they would turn anyone away. Even at the peak of high season they were plenty of vacancies available at refugios along the way, and given the fiasco that online reservations turned out to be with Fantastico Sur you might be better off turning up in person. As of 2017, credit cards are accepted at all of the refugios along the W-Circuit. There are no ATMs so you should carry some cash with you as a backup in case the network cannot connect or if you have to make a payment at a campground. You'll also have to pay for your catamaran ticket in cash.
Some of the buses will continue to Pudeto. If you're starting your trek with Glacier Grey you'll want to head there. Once at Pudeto, you will board a catamaran ($18,000 one-way) across Lake Pehoé to Paine Grande. You'll be treated to spectacular views of the Cordillera Paine range as you cross the lake. The view from the outside deck is worth dealing with the cold wind on a clear day.
Refugio Grey is approximately a 4.5 hour hike from Paine Grande. Patagonian weather patterns can be chaotic. You may encounter sunny 70-degree weather shifting to sleet blowing in your face within a 10-minute window. You should have warm gloves a rain poncho ready at all times. Hiking poles are also a necessity to brace yourself against the wind. The trail will take you along a ridge above Lago Grey.
The refugio and campgrounds are sheltered and not directly on the lake but are only a brief walk to lookout points where you can see the ice sheet.
There are spots where you can climb down to the glacial water itself. The water can be safely drank without filtration.