When I first got Nugget he was really bad at it. He was always at my feet scratching and nipping, I had to wear boots inside to protect myself.
I tried the squeel, and the NO! and time out, but waht really seems to work is a loud thump. I read somewhere that this is how they would communicate with each other, their way of giving a warning, so I do it, the louder the thump the better it works.
If he ignores the thump he goes into time out. It seems to work for everything. Nuggetwas a terror, humping, spraying, nibbling, chewing, weeing on the couch, butafter 2 weeks of continuous thumping and time out Nugget is now an angel :innocent- he hasn't sprayed on me for over a week or jumped on the couch - it is awesome (touch wood)