Be a good friend:
In a study appropriately titled "Very Happy People," researchers sought out the characteristics of the happiest 10 percent among us. Do they all live in warm climates? Are they all wealthy? Are they all physically fit? Turns out, there was one—and only one—characteristic that distinguished the happiest 10 percent from everybody else: the strength of their social relationships.
Will Wilkinson admits it's harder than it sounds:
If I had to name my single greatest flaw, I'd say it's dereliction of friendship. I don't actively cultivate new friendships. They either happen to me or they don't, and mostly they don't because I don't put in much effort from my side. I'm not sure why, but I think it's mostly because I find the idea of extending a hand stressful. Worse, I'm terrible at keeping in touch with old friends. After too much time without calling or emailing or texting or anything, I feel really embarrassed. And then, perversely, that embarrassment makes me more not less averse to reestablishing contact.