This is a good article from Psychology Today: Friendship: The Laws of Attraction.
An excerpt:
But according to social psychologists Carolyn Weisz and Lisa F. Wood at the University of Puget Sound, in Tacoma, Washington, there’s another component to best friendship that may trump even intimacy: social-identity support, the way in which a friend understands, and then supports, our sense of self in society or the group. If we view ourselves as a mother first and a belly dancer only on Saturday mornings at the local dance studio, our best friend is likely to be another mom because she supports our primary social-identity (as opposed to our personal identity as, say, someone who loves film noir or comes from the Bronx). Our social-identity might relate to our religion, our ethnic group, our social role, or even membership in a special club.
Also some interesting tips on how to maintain friendships:
From young adulthood onward, our notion of what makes a good friendship changes very little, but our capacity to maintain one does. It’s a poignant reality; we know what it means to be and have friends, but after we graduate from college and go our separate ways—launching our careers, getting married, having children, getting divorced, caring for aging parents—we’re often unable to muster the time and energy to maintain friendships we profess to value. Like anything else in life, if we want to remain friends with someone, it requires a little work. Simply put, we must show up.
Communication facilitates the first two essential behaviors: self-disclosure and supportiveness, both necessary for intimacy. We must be willing to extend ourselves, to share our lives with our friends, to keep them abreast of what’s going on with us. Likewise, we need to listen to them and offer support.
Interaction is the third essential in tending to a friendship. You’ve got to write, you’ve got to call, you’ve got to visit. Find the nearest Starbucks and take time to catch up. “The specific activity doesn’t matter,” says Oswald. “The important thing is to interact.”
The last and most elusive behavior necessary for keeping friends is being positive. Social psychologists tout the necessity of self-disclosure, but that doesn’t mean an unrestricted license to vent. At the end of the day, the intimacy that makes a friendship thrive must be an enjoyable one, for the more rewarding a friendship, the more we feel good about it, the more we’re willing to expend the energy it takes to keep it alive.
