Castelia City - tall building near Pokémon Center
You can get a massage each day in the place where darthdestiny told .
I used this guide : http://www.serebii.net/games/happiness.shtml
and others relating to it .
I recommend going to Icirrus City in the pokemon fanclub and talk to the girl to know how happy your pokemon are .
Occasionally use vitamins and always hold a soothe bell and make that pokemon lead your party !!
Have a Happy Journey!! :)