>The friendship system remains essentially similar to Generation III, though the conditions are altered slightly. The Luxury Ball now causes a Pokémon to gain a separate boost in friendship when they level up and while walking compared to Pokémon in other Poké Balls.
>In Pokémon HeartGold and SoulSilver, the player can gauge their Pokémon's friendship based on the phrase that appears when they are interacted with outside of their Poké Ball. Daisy also makes a return and visiting her in Pallet Town will let her groom one of the player's Pokémon between 15:00 and 16:00 every day, increasing its friendship. The haircut brothers will also boost a Pokémon's friendship and they can be visited on any day of the week besides Monday.
>In the table below, the first and second values separated by slashes show the changes for most Poké Balls and Luxury Balls, respectively. Note that holding a Soothe Bell will apply a rounded-down multiplier of 1.5 to only positive changes and that use of Luxury Balls will not reduce the effects of negative changes.
Happiness rate phrases can be found here.
The chart shows everything that affects happiness. A soothe bell multiplies any increase by 1.5 (rounded down). Evolving to Espeon requires leveling up at 220 or greater happiness during the day. You can get happiness rates from a woman in Goldenrod City.