It seems such common sense, but so does a lot of things once they are studied. Here is a really interesting paper on the dynamics of how happiness spreads through your social connections.
To me, the summary seems to be to live close to your friends and family and make them happy. If you do, you increase your chances of happiness also.
Dynamic spread of happiness in a large social network
This also follows on from other work that shows the spread of obesity, smoking, and other health effects.