Three bases, in descending order of convenience and ascending order of price: Puerto Natales, the hotels along the park road, and the refugios and campsites on the trails themselves.
Puerto Natales — the basecamp
The corrugated-iron port town about 150 km from the park by Route 9 North, where nearly everyone sleeps before and after a trek: gear rental, supermarkets, buses and the widest range of prices. Day-tripping the park from here means roughly two hours on the road each way.
Inside the park — refugios and campsites
Beds on the W and the O are run by two concessionaires, Las Torres on the eastern side and Vértice on the west, with camping alongside most of them. They must be booked before you walk and December to February goes months ahead; it is the most expensive way to sleep in Chile and the only way to do the circuits.
The park road — Cerro Castillo, Lago Sarmiento, Río Serrano
Hotels and estancias strung between Puerto Natales and the park entrances, from working sheep stations to lodges with the Cuernos in the window. They cut the morning drive substantially and almost all of them assume you have a car.
Practical: Punta Arenas, and booking early
Flights land at Punta Arenas, about 250 km and three hours south, with several bus companies covering the gap through the day from 07:00. Book park beds and anything in December to February as far ahead as you can — this is not a place that rewards improvising.