As social creatures, humans benefit from turning our sociability to higher ends. The Buddha, after all, did make the sangha, the spiritual community, one of the three cornerstones of his path; and Christ told his disciples, "When two or more are gathered in my name, there am I in the midst of them." As these words imply, a group practicing together creates a mystical field, a field of grace. The Sanskrit name for that phenomenon is satsang, usually translated as "truth-company," or being in the company of the wise. And satsang, according to several texts of yoga, is one of the great doorways to inner freedom. As is the case with meditation and asana, the more you practice satsang, the more likely you are to experience its power—and you don't have to join an existing community in order to do this. Some of the most powerful satsangs are the ones we create informally.
An informal satsang group should be small—five to seven is a good number, and you can easily form one with three, two, or even just one other person. All it takes is (1) a decision to have a spiritual dialogue; (2) some sublime and true words to spark your insight; and (3) a shared agreement on the ground rules.