Heavily reinforce them being OFF the couch while you are around...(read the first part of this article:)http://www.petplace.com/dogs/keeping-th ... page1.aspx
and use something to keep them from gaining access to the couch while you are away. (second part...uses aversives-things that make it uncomfortable to lay there)http://www.petplace.com/dogs/keeping-th ... page1.aspx
Basically, make being off the couch as much fun as being on the couch was before. Use treats, toys, etc to reward good behavior. Provide alternate areas that are comfy, to sleep on for them...and reward them for using those instead.
At the same time, be consistent in not allowing them up on the couch when you're not around to reward them. Block off the couch with boxes...great idea. Use anything that makes it uncomfortable for them to be up there (plastic carpet runners upside down work well too)...yeah, it's aversive, but you have to make it so it's NOT comfy anymore.
If that's a problem...(my parent's dogs just knock the stuff off and sleep there anyway)...you'll have to keep them from even getting into that room...close doors, crate them, etc. Prevention can be the best medicine.
My Aussies think nothing of jumping onto the kitchen table to see watch us drive into the driveway...so while we're out...we lock them into the bedrooms...so I don't have to use aversives on the table.
It won't be easy, or overnight that this happens...they obviously enjoy lying on the couch...so you'll have to be consistent with your rewards, your aversives (if you chose to use them) and your prevention.
"I don't have any idea if my dogs respect me or not, but they're greedy and I have their stuff." -- Patty Ruzzo
"Dogs don't want to control people. They want to control their own lives." --John Bradshaw