wcook:How many social networks does your organization maintain a presence on? Did you begin with an individual profile? How did you build up your presence? What would you recommend to other nonprofits just getting started with social networking?
This obviously depends upon where your current donors are.
The first step would be to search social media sites (Start with Twitter and Facebook) for relevant keywords. For example, the American Heart Association would search for "heart disease", heart attack", "high cholesterol" and so forth.
Then, create accounts on the two sites that returned good search results and start developing conversations with like-minded people. Most of my clients started slowly, just listening to what people were talking about and then contribute to discussions when appropriate. They've built up their presence with my help and some hard work on their part.
The biggest mistake you could make is to approach social media like it's a "market to marketed to" - like a massive free email list. Facebook and Twitter are places where millions of people have meaningful discussions on just about every topic you can imagine. If you approach these sites with the goal of adding value to the community, you will soon have a successful experience.
Hope this all helps.
John