Instructions
Walk or ride your bike with Latias everywhere you go. Latias gains one happiness point for every 256 steps taken.
Battle often to level up Latias, as its happiness grows with each level of increase. Be careful to prevent Latias from fainting in a Pokemon battle, to keep its happiness from decreasing.
Bring Latias to major Pokemon Battles, and its happiness will greatly improve, because it will feel more important to the team. Winning battles against the gym leaders, the Elite Four and the current Pokemon Champion will greatly increase Latias's total happiness.
Feed expensive stat-altering Vitamins such as HP Up, Iron, Zinc and Protein to Latias. Not only will its speed, defense, special attack or other abilities improve, but it will become much happier.
Pay for a grooming session for Latias from the Haircut Brothers in Goldenrod City. Although the older Haircut Brother is slightly more expensive, Latias gains more happiness from his grooming expertise.
Refrain from using bitter items on Latias. Feeding it Energy Powder, Heal Powder, Energy Root or Revival Herb will greatly lower its happiness.