Instructions
Place the Pokemon that you want to become friends with in your active Pokemon party. Just the act of walking around with the Pokemon in your party will slowly increase your friendship level.
Use the Pokemon frequently in Pokemon battles to gain experience and increase its level. Each time a Pokemon levels up, your friendship meter also increases. Using the Pokemon during important battles, such as Gym Leader battles or Boss battles, also greatly increase your friendship. Heal the Pokemon or remove it from battle before it is knocked out to prevent a loss of friendship.
Feed berries to your Pokemon that increase friendship, such as a Pomeg or Kelpsy Berry. Each berry that increases friendship also lowers one of your Pokemon's effort values. For example, a Pomeg Berry lowers the Pokemon's HP effort value. Berries can also be used to make Poffins, which are baked treats that increase your Pokemon's happiness.
Take your Pokemon to a Pokemon masseuse or hairstylist to pamper it. Massages greatly increase your Pokemon's friendship levels, while haircuts increase your Pokemon's friendship depending on how well the Pokemon likes the hairstyle.
Feed vitamins like HP Up and Carbos to your Pokemon to increase your friendship value.
Capture the Pokemon with a Friend Ball to have the Pokemon begin with a base friendship value of 200. Catch the Pokemon with a Luxury Ball to have a Pokemon that gains friendship levels twice as fast.
Give your Pokemon a Sooth Ball as a Hold Item. This will cause its friendship levels to increase twice as fast whenever friendship is gained.