Stand Couches on End
If you ever have to maneuver a couch down a hallway and through a door, you may find it almost impossible to carry it horizontally and make the turn into the room. Before you enter the hallway, place the couch on its end and slide it to the doorway. You'll almost always be able to hook it through the door. If it's a bit taller than the door opening, start the top away from the door and gain several inches of clearance.
Moving and lifting straps (Shoulder Dolly, shown here, is one type; available at amazon.com) take the weight off your back by relying on leverage and large muscle groups. They also leave your hands free to maneuver awkward items. However, they can be tricky to use on stairs because the weight shifts completely to the downhill mover.