PAX partners with local hotels to provide reduced rates and a reserved block of rooms through a third party travel system, OnPeak. To get a reduced rate, one must book through the official PAX OnPeak link for the associated show.
Many PAX attendees choose to share their room to reduce costs of their PAX trip. Room sharing is organized via the official PAX forums. This also often acts as a method of meeting new people or getting extra hangout time with people one might already have met.
PAX East 2013 Hotel Partners
Details for the hotels that have blocks of reserved rooms has been published as a spreadsheet here, as created by PA forum member vttym.
To read about others' experiences with these hotels and to ask questions, check out the hotel discussion PA forum thread.
PAX Prime 2012 Hotel Partners
Go to the OnPeak Reservation Site when you're ready to book your hotel.
Hotel Status is based on availability for the bare minimum for PAX (Friday Night and Saturday Night).