I read once about using a set of keys lobed in the air to land BESIDE the culprit and that was the only thing that would work with our hound, Blue, after a few time the jingle of the keys was enough to remind him of his manners. Brutus on the other hand has enough respect to stay off the sofa, except on the odd time that i've found him spread right out on it on the morning
(it happenes pretty rarely and who can blame him for testing that limit)
Good luck :)
Dani and Brutus