To an extent, it is up to the player to find out what all of their companions favor. Still other companions care more about the manner in which they are treated than the 'alignment' of your choices (although that doesn't mean that they don't take alignment into account) Kreia, for example, does not like having her opinions ignored or disregarded. Certain companions like Light Side actions whilst others like Dark Side actions, and some like both.
This influence system is based off of actions as well as dialogue, and is variable on a companion-by-companion basis. KOTOR 2 has an influence system which activates from the point the player steps onto the Harbinger at Peragus. This answer from the wiki should be helpful:
