Hobbies And Interests
Keep Them Close
The Pokemon placed in the top slot of your traveling party of six Pokemon walks alongside you outside of its Pokeball, and this is one of the best ways to increase your friendship with that Pokemon. For every 256 steps you walk alongside a Pokemon, its happiness increases. If you give your lead Pokemon the Soothe Bell item, its Happiness will increase even faster.
Battles
Every time your Pokemon gains enough experience points from battles to reach a new level, it will receive Happiness points. A Pokemon holding a Soothe Bell will get extra points, while a wild Pokemon caught in a Luxury Ball will also gain more Happiness than usual.
Berries and Vitamins
There are a number of consumables you can feed to your Pokemon to increase their stats or battle effectiveness, which also increase their Happiness. EV Berries such as Pomeg Berries, Kelpsy Berries, Hondew Berries and Tamato Berries give your Pokemon a boost in Happiness whenever they are eaten. The same goes for stat-boosting Vitamins like Iron, Calcium and Rare Candies.
Grooming
"Pokemon SoulSilver" features a number of places you can take your Pokemon for grooming, which increases its Happiness. Between 3 and 4 o'clock each day you can visit Daisy in Pallet Town to groom your Pokemon, while the Haircut Brothers in the Goldenrod Tunnel of Goldenrod City can give your Pokemon a haircut and a Happiness boost on weekdays excluding Mondays.
Things to Avoid
While using your Pokemon in battle is a good way to build up your friendship, if it is defeated in a fight and faints, it will lose Happiness points. If your Pokemon is losing a battle, swap it out for a fitter one. Trading a Pokemon resets it to base Happiness, and the use of items like Energy Powder, Heal Powder, Energy Root and Revival Herb also impact negatively on your Pokemon's Happiness.