I’d suggest you look at basic accounting (balance sheets etc, I’d say Junior Cert level might be enough to grasp the core aspects). Every aspect of a business feeds into its balance sheets, it doesn’t matter what sector the business is in accountancy is at the core.
While I wouldn’t take it as Gospel this might give you an idea http://en.wikipedia.org/wiki/Balance_sheet.
It’ll depend, to a degree, on how granular you want your game to be, i.e. manager in a shop that may have to deal with unhappy customers versus a manager in an office away from the shop floors. But you’ll still have to balance your "books".