There are 4 endings total but I only needed to unlock two of them.
Morrigan offers a ritual to spare the life of the Wardens. You either need to be a male Warden or talk Alistar or Loghain into doing this. (Also unlocks A Dark Promise)
Other three endings:
Involves sacrificing one of the Grey Wardens. (Also unlocks The Ultimate Sacrifice)
You can get this all on the same campaign by creating a save file before the Landsmeet to choose either Alistar or Loghain and then one before talking to Morrigan at Redcliffe.