Bear off to a broad reach (10-20 degrees up from a dead-run is best).
Grab the lazy sheet in front of the main boom.
Release the downhaul, or the active sheet, completely, and gather the sail behind the mainsail using the lazy sheet.
Ease the halyard as fast as the sail can be gathered.
Stuff the sail down the companionway or forward hatch as you gather. A spinnaker sock can be pulled over the sail to keep it from blowing out of control. Release the sheet and pull the sock down, then gather. It's easier to put the sail in a bag later.