Try this:
Ways to induce happiness:
Walk 256 with the Pokemon in your active Party. (+1 for all happiness values)
Give the Pokemon Vitamins [HP Up, Carbos, Iron, Protein, Calcium, PP Up] (+5 0-99, +3 100-199, +2 200-249)
Usage in Important Battle [Gym Leaders, Elites, Red] (+3 0-199, +2 200-249)
Level Up the Pokemon (+5 0-99, +3 100-199, +2 200-249 per level)
This may help : http://bulbapedia.bulbagarden.net/wiki/Happiness