Here are some useful tips I found on "building communities".... it's fairly academically based, however, it makes interesting reading.

Lists of Design Principles for Communities

1. Axelrod's (1984) requirements for the possibility of cooperation:
a. Arrange that individuals will meet each other again
b. They must be able to recognize each other
c. They must have information about how the other has behaved until now

2. Ostrom's (1990) design principles of successful communities:
a. Group boundaries are clearly defined
b. Rules governing the use of collective goods are well matched to local needs and conditions
c. Most individuals affected by these rules can participate in modifying the rules
d. The right of community members to devise their own rules is respected by external authorities
e. A system for monitoring members' behavior exists; this monitoring is undertaken by the community members themselves
f. A graduated system of sanctions is used
g. Community members have access to low-cost conflict resolution mechanisms

3. Godwin's (1994) principles for making virtual communities work:
a. Use software that promotes good discussion
b. Don't impose a length limitation on postings
c. Front-load your system with talkative, diverse people
d. Let the users resolve their own disputes
e. Provide institutional memory
f. Promote continuity
g. Be host to a particular interest group
h. Provide places for children
i. Confront