Instructions
Give your Pokemon a large amount of status-improving vitamin items. Although Calcium, Iron and Protein are expensive, they quickly improve the creature's friendliness stats.
Keep the Pokemon in your party at all times. Its happiness rating improves slightly after taking a predetermined amount of steps with the Pokemon.
Level up your Pokemon often. By growing your Pokemon to stronger levels, it will start to bond with you.
Give your Pokemon a Sooth Bell item to hold. Pokemon that hold a Sooth Bell gain extra happiness points for every action that improves their friendly mood.
Catch any Pokemon for which you intend to increase its friendship level in a Luxury Ball. A Pokemon caught in a Luxury Ball is naturally happier than a Pokemon caught in any other Pokeball type.