use it a lot, go to the haircuter and feed it with berries that gives increased happiness.
Chat with our AI personalities
Max out it's happiness.
just max the happiness hope this helps
Any level, just get it to max happiness.
Once traded from Diamond, Pearl, or Platinum, you can evolve it with max happiness.
In goldenrod, by the bike shop there is a house. Talk to the lady inside. She will say something like: Your Pokemon is still warming up to you (low happiness) Its quite cute (kinda low happiness) Seems to like you a little (kinda high happiness) It really Trusts you (Max happiness)