How do you max out happiness in Pokemon heartgold and soulsilver? - Answers

Either put it in the front of your party and battle thousands of trainers or wild Pokemon, OR An easier way is to get the Soothe Bell and just run back and forth until you gain your pokemons Happiness. Every step while holding soothe bell makes it happier. And in HG/SS just walking with you also raises happiness. But don't let it faint or put it in your Box because it will lose all happiness.