There's been no detailed presentation of the whole Mars architecture; Musk has promised to present at least an overview this September at the International Astronautical Conference.

In the meantime, it's known that there's a high-performance methane-fueled engine in development as part of the project ("Raptor"), with some component tests already underway at test facilities, and several dropped hints about components (including rockets substantially more powerful than the Saturn V used for Apollo lunar missions), but not enough publicly released to determine much about how operations would work.

As rst has mentioned, details on how the Red Dragon would return from the Martian surface have so far been quite sketchy. However, the basic outline for a proposed sample return mission involves having a Mars Ascent Vehicle pop off the top of the Red Dragon capsule to get the payload into low Mars orbit. Once there it jettisons the ascent stage and ignites a second stage to place it into a trajectory for trans-Earth injection. Essentially, it's packing a small two-stage rocket for the trip home. [1]

It'll be interesting to find out if the payload capacity of the MAV is actually enough for a crewed capsule to be launched to rendezvous with an orbiting vessel (a la The Martian), or if that would require a much larger descent vehicle in the first place.

[1] http://www.space.com/24984-spacex-mars-mission-red-dragon.ht...

Perhaps something involving potatoes.