[Michael Romanos]

The word or words you use can be anything. For example you can say 'banana' or 'cantabrian' to a dog and it could mean shake hands or wave. It is not the actual word that a dog gets to understand but a word associated with what action or behaviour the handler wishes to have the dog follow.
As I understand it, a wave is very close to a dog placing his/her foot on you while facing you in a sitting down position. But I have also seen a dog wave in a very marked manner so that they actually wriggle their leg and their foot flaps. However the norm, is for a dog to bring up one leg from sitting - much like shaking hands but with no extending of a hand from the handler, However again, a handler may wave his/her hand and the dog correspondently copies the same kind of action.