What platform should you use for your online community? What content should be members only, and what should be for public consumption? Hear strategist Dorie Clark's take, in this excerpt of a recent talk she gave to the New England Society of Association Executives. Clark is the author of the forthcoming What’s Next?: The Art of Reinventing Your Personal Brand (Harvard Business Review Press, 2012). Learn more at www.dorieclark.com.