I've used the following formula (adapted from Dr. Julian Simon's work) for the past 10 years, with a good degree of success:
Happiness = Perceived State / Expected State
You can either improve the numerator or reduce the denominator.
Happiness = f(Reality, Perception) / f(Perception of Peers' State, Personal Needs)
By this logic, one needs to learn to ignore what others (particularly one's peers) have and focus more on the question "What do I want?" Trying to increase happiness by changing Reality (which is what most people do) is a very inefficient strategy, especially after your basic needs are met.