Instructions
Keep the Digimon in your party during battles. Every time you win a battle, your Digimon's friendship level will increase. But be careful: If the Digimon faints during the battle, its friendship level will go down. Try to choose easy battles, and use a healing potion on the Digimon if it takes a lot of damage.
Put your Digimon on a "Digifarm" and talk to it. It you talk to it a lot, its friendship level will rise. If you ignore it, its friendship level will drop.
Accomplish quests that your Digimon gives you while you are talking to it at the Digifarm. Often these quests entail retrieving an item from a distant place. After you accomplish the quest, the Digimon will like you more.
Use the massage glove on the Digimon while it is at the Digifarm. You can also buy certain farm goods that will increase the Digimon's friendship level. Items to buy include the keychain, cell phone and digital camera.