Great question. A few thoughts:
Rather than think about "guidelines for a community" that are focused on the design, construction and management sides, you may want to approach this slightly differently at first:
1. Core Audience: Making sure there is a crystal clear, maniacal focus on the target audience. Who they are, what they do, where they work, what they like, how they consume media, etc.
2. Value Exchange: The best experiences are one where there is a very clear articulation of exchanging value. What's in it for the participant? Why should she share, engage, interact? When there's an obvious reason for reciprocity, the vibrancy of the experience will take off.
3. Think content, and experts: To fuel the experience, the more you facilitate linkages between target audience contributing, experts/influencers contributing, third-parties contributing, your brand contributing, and likely newly created content, the better.
4. Broad, distributed engagement opportunity: People are getting more and more overwhelmed by new sign-ons, and multiple destinations. How can you share sign-on/registration with other initiatives (like, LinkedIn on the B2B side); and how can you distribute the experience so individuals can keep updated/observe from where they are? Getting a set of established web influencers to participate will do two things: one, it will add more scale, amplification, and awareness because they will extend your reach to their communities; and two, they will be providing valuable content and opinions to increase the authenticity and transparency of the experience.
5. Experience itself: Then you can focus on some core experience requirements, like simplicity of design and navigation, plethora of commenting/engagement/voting/liking tools, and a multitude of following and sharing options.
Hope that helps.