First by recognizing them and their importance. Look for jobs that exist in several functions, business units, or geographic areas, suggests George Por, head of a Santa Cruz, California, firm called Community Intelligence Labs, who has helped Intel and Dow Chemical support communities of practice. Managers can do a lot for these groups. Communications systems are usually laid out along existing departmental lines. There are big benefits from linking people who may unknowingly duplicate one another's efforts or walk away from projects too big to tackle single-handed.
Communities of practice are the bridge.
Fertilize the soil, but stay out of the garden. It won't work. You'll get what the community wants to deliver. For its members, boundaries exist to be crossed, just as mountains exist to be climbed. Information wants to be free.