There are benefits to being a friendly Trainer and having a good level of friendship with your Pokémon in Brilliant Diamond and Brilliant Pearl. Friendship Level can improve a Pokémon's performance in a battle, so you'll want to increase your Friendship Level with your Pokémon as quickly as possible.
There are many ways to do this, but one of the most basic things to know is that you can use the Poketch app to check your friendship level.
To quickly improve your friendship levels with a Pokémon in Shining Diamond and Shining Pearl, you'll need to get your hands on the Bell. The Bell can be found on Route 212 in Pokémon Brilliant Diamond and Shining Pearl. Here you will find the Pokémon Mansion. If you enter, you will find an NPC maid in the second room on the left. Talk to her and she will give you the Soothe Bell for free.
After arriving in Hearthome City and reaching Friendship Square, you will find a park where you can walk with your Pokémon. Talk to the NPC at the desk and you can choose a Pokémon to follow will also improve their friendship level.
You can also have your Pokémon give a massage in Veilstne City, in the southwest corner of the city. However, you can only enjoy a limited number each day, so keep that in mind.
