For my personal narrative, click here: http://www.patagoniaadventurecycling.com/news/2015/2/8/hiking-the-o-the-3-zones-of-pestilence-and-the-hugarian-horse-tourist

Overview
If you are a backpacker, or just an outdoorsy person, you owe it to yourself to hike the “O.”  It is one of the most spectacular, iconic treks in the world, its international reputation well-deserved.  You will see glaciers and snow-capped mountains, the classic view of the Torres themselves, barren landscapes of grass and brush dusty in the sun, and verdant valleys.  Each day will bring a slightly or sometimes drastically different landscape.  Having hiked both the “W” and the backside of the range, together which comprise the Torres del Paine Circuit, or “O,” as it is known, I can emphatically recommend that you take slightly more time to hike the full circuit.  The “W” has some spectacular views, but not the most spectacular (that title belongs to the view of Glacier Grey from John Gardner Pass); it also has the most people and crowded campsites. 

How do you get there? 
First, you will need to make your way to Puerto Natales.  If you are on a bicycle, this is easy: Take Ruta 40 south from El Calafate or Ruta 9 north from Punta Arenas.  If you are not a bicycle tourist, there are several more traditional ways to get there: 1) You can fly into Punta Arenas and rent a car, then drive the 2-3 hours to Puerto Natales; 2) You can fly to Punta Arenas and take a bus to Puerto Natales, which is cheap and fairly comfortable; 3) You can fly into Puerto Montt and take the 3-day Navimag ferry to Puerto Montt.  You will have to book this in advance.  I have not done it, but supposedly you get some amazing views of mountains and glaciers during the voyage.  It is fairly spartan, though, so do not expect anything plush.

Once you are in Puerto Natales, the easiest way to get to the park is to take a bus.  You can book the bus through your hostel or at a bus company kiosk inside the bus station.  Most people take the 7:30am bus, but there are later options as well.  It takes about 3 hours to get there.

How many days does it take?
Most people take anywhere from 6 to 10 days for the “O.”  I found 7 days to be about right, but it is certainly possible to finish it fairly easily in 6 or, if you put in quite a few long days, 4 or 5.  9 or 10 days would be very easy and include a large portion of down time.  I often started hiking at 10am and was done by 2:30pm.  The first and last days include transportation to and from Puerto Natales.  Blisters, injuries, and bad weather do happen, so you might want to include an extra day in your plan just in case.

Where should you start?
You have four options: 1) You can begin from the administration office, where you pay the fee, and hike directly from there to Hotel Torres or Campamento Seron; 2) You can transfer to a different bus, ride to Hotel Torres, and begin there; 3) You can get back on your bus after paying your fee and continue on to the restaurant/catamaran dock and hike the long way into the park from there, saving money and adding a significant chunk of miles; or, 4) You can take the catamaran from there to Refugio Paine Grande.

I strongly recommend you choose option 4, which does have the disadvantage of costing $30,000 Chilean Pesos (round trip), but it allows you to begin with the crowds and finish with the isolation and stunning views of John Gardner Pass and Glacier Grey.  Most people start at Hotel Torres, so if it is important to you to match your trek to strangers’, then you should start there.  Trust me, though, Paine Grande is where you want to start.

Which direction should you hike?
Counterclockwise. Again, if you start at Paine Grande, you want to finish with Glacier Grey, which requires you to walk counterclockwise.  Additionally, this gets you through the crowds at the beginning so that you can finish with the more isolated campsites at Dickson, Perros, and Paso.  You knock out two of the big climbs early on and build up to the biggest for your second to last or third to last day, depending on many days you take.  Lastly, John Gardner Pass is much easy coming from the northwest than from the southeast, and the reward at the top – your first glimpse of Glacier Grey – far outclasses your anticlimactic view going the other way.

What food do you need?
You can buy breakfast, a to-go lunch, dinner at Paine Grande, Chileno, Torres, and Dickson.  You can buy snacks and food to cook at Chileno, Torres, Seron, Dickson, Perros, and Grey.  You cannot buy anything at Italiano, Torres, or Paso.  I brought oatmeal for each breakfast, trail mix and snacks for lunch (note: you cannot cook on the trail so do not plan on cooking lunch), and pasta, acquired at a grocery store in Puerto Natales, for dinner.  You will not find freeze-dried food in Puerto Natales.  I did, however, treat myself to breakfast at Chileno.  It honestly was not worth it.  I also brought a small amount of pisco, which I found myself pretty uninterested in drinking, but it was good for sharing with new trail friends.

What clothing do you need?
You will experience cold blowing wind, a big hard sun, dust, and possibly rain, sleet, or even snow.  I recommend you bring a set of hiking clothes – zip-off pants, microfiber or wool shirt, quick dry boxers (no cotton), socks – and wear them every single hike, not matter how nasty they get.  Bring a pair of pants, boxers, socks, short sleeve shirt, and a long sleeve shirt as your camp wear.  Do not, under any circumstances, wear your camp clothes on a hike.  Keep them clean.  This is crucial.  Additionally, bring a rain jacket, a fleece, hat, gloves, and a warm synthetic down coat.

What gear do you need?
I brought my own gear, but you can rent most gear in Puerto Natales.  I have heard they occasionally run out, so I wouldn’t necessarily count on it.  You will need a backpack, camp stove, fuel canister, tent, sleeping bag, sleeping pad, toilet paper (the bathrooms do not always have toilet paper, FYI), utensils, a bowl, a cup, sunscreen, bug spray, chap stick, duct tape (justin case), one large water bottle and sunglasses.  I always bring a book, a journal, and a pen, too.  You do not need a water filter.

My recommended itinerary:

Day 1 – Hike to Campamento Italiano, dump your stuff and set up your tent, climb up to Mirador Britanico, and return to camp (~11 miles)
Day 2 – Hike to Campamento Torres (note: you must make a recommendation in advance for Torres and Chileno) or Chileno, if Torres is full (~13 miles)
Day 3 – Wake before dawn and hike up to Base de las Torres (1k up a steep climb), watch the morning sun hit the towers, take photographs, return to camp to grab your stuff, hike down to Hotel Las Torres for a decadent lunch and wifi, if you are so inclined, then hump it to Campamento Seron.  It is OK to arrive to Seron late in the day as it is not particularly pretty and there is nothing to do there.  Take your time in the morning.  (~13 miles)
Day 4 – Hike to Campamento Dickson (~11 miles)
Day 5 – Hike to Campamento Perros (~7 miles)
Day 6 – Hike over John Gardner Pass, which will not be nearly as hard as you expect based on the elevation profile, spend a lot of time bundled up, pondering Glacier Grey, camp at Campamento Paso (~5 miles)
Day 7 – Wake up early and take your time hiking the 6.2 miles from Paso to Grey.  Note that the park map incorrectly states this distance as 6km; it is 6km to Campamento Guardas, which is only for park employees, and another 4km from there to Refugio Grey, so 10km in total. You will have repeated, breathtaking views of Glacier Grey.  Enjoy them.  I did this stretch the same day as the pass, skipping Paso for a night at Grey, and regretted it.  If you stay at Grey, it will be like coming down from a bad acid trip.  There will be hordes of loud people.  You will be camped in a herd of tents.  People will get drunk and shout all night, they might play music from portable music players.  So keep the pass day short, take your time on Paso to Grey, then crank out the last 6.5 miles to Paine Grande in time for the 6pm boat.  You will get into Puerto Natales late, so it is best if you have a reservation waiting. (~12.5 miles)

As you can see, it would be very easy to reduce days 5 and 6 to 1, but they are the most beautiful days, so if you have the time, I suggest you take it easy and sink into the scenery.  Make it happen!