Dragon Age 2 Quest Reference: Act 1 - Main Plot - The Deep Roads Expedition
Requires: Complete these quests - A Friend in the Guard, Long Way Home, Tranquility, Blackpowder Promise, Shepherding Wolves, Enemies Among Us, Wayward Son and Act of Mercy. Pay the 50 sovereigns to Bartrand or complete Friends in Low Places. And deliver the maps from the Tranquility quest to Bartrand.
If you haven't completed side quests or companion quests, this is your last chance before moving on to Act 2. Also, you need to add Fenris and Isabela in Act 1. Talk to Bodahn before leaving and agree to his request to find Sandal. You'll find him anyway so might as well earn the XP for it.
As soon as you're on your way expect to be attacked. You'll find Sandal in the first narrow section. Be sure to check the chest at the end of the passage. Basically the path continues the same way, one battle after another, until you meet the Hunger Demon, leader of the Profane. If you accept his offer you'll get to leave faster without fighting more. But, you'll miss out on a lot of XP, gold and items that you can get off enemies and in chests. If you do take up the leader on his offer, he'll demand that you honor your end after the next monster battle, but go ahead and have Varric kill him, it won't have negative affects.
You'll no longer have Bethany or Carver after Act 1, but depending on your choices different things will happen to them. If you bring your sibling along, he or she will get sick with the Blight. If Anders is in the party, he'll offer the option for Bethany/Carver to become a Grey Warden. If you refuse, he or she dies. If your sibling becomes a Grey Warden, you'll see them again in the last fights in Acts 2 and 3. If you leave them at home instead of taking them on the Deep Roads Expedition, Bethany will join the Circle or Carver will join the Templars. If they come with you and Anders isn't there, he/she will die.