I have a Rayquaza that I got by trading and I wanted to teach draco meteor to it.
But the tutor lady in blackthorn city says it doesnt fully trust me yet.
but I talk to it and some people that I talk to, say that he is alredy happy.
Maybe it's not fully happy yet. Give it a soothe bell and walk around and battle with it for a while. It may take a few hours to get it to max happiness.
There are also berries that improve happiness, but make your stats (EVs) fall. You can get the stats back up from more battling though.
See also: http://pokemondb.net/pokebase/6847/what-is-the-quickest-way-to-make-a-pokemon-happy
I dunno for sure, but I think feeding it its favorite poffin helps. Worth a shot!
go get it massaged by someone once a day, it is one of the best ways to give it happiness