I recommend checking Help section in Book [TAB] for more details on Affection and stats.
If i recall correctly, affection can be raised via :
- hActs
- following (while fapet is following player, after a certain amount of time, it will get a small affection boost)
- feeding (gives a lot of affection, even more if it's the preferred food, check fapet's taming recipe for favorite food)
- pat (quick command, unlocked after taming more then about 6 fapets of same specie. This animation changes with Affection level).
I hope this helps,
Cheers,
~NK