Chris Brogan is President of New Marketing Labs , a new media marketing agency, and home of the Inbound Marketing Summit  conferences and Inbound Marketing Bootcamp educational events. He works with large and mid-sized companies to improve online business communications like marketing and PR through the use of social software, community platforms, and other emerging web and mobile technologies. Chris is also co-author of the book Trust Agents , with Julien Smith. For more information, read his blog  or follow him on Twitter .
What are the first three things someone should do if they have little to no social presence and want to change that?
Start by listening. Use social media listening tools (google "Grow Bigger Ears" for starter advice), and start seeing what people are saying. Where are they saying it? Are they talking about you on Twitter, on Facebook, on blogs? Once you've listened, build some accounts and profiles so you can join in the conversation. At some point, consider setting up a place for your social media conversations, like a blog or Twitter, or whatever makes most sense for your business.
Can you share some tips for managing a large number of followers on Twitter? How do you keep engagement levels high?
Comment and reply as often as you can to what people are talking about. Give full replies instead of simple "@person 'yes'" types of replies. Make sure that you're using tools like Seesmic Desktop or Tweetdeck to manage your information flow. The web-based tool doesn't cut it, and you need power tools once you get to a certain volume. Stay human. No matter how many people are following you, using robot tweets isn't okay.
What are some ways to measure return on investment from social media marketing?
It depends what one is investing and how. Are you investing in resources? Are you talking about time investments? Look for how revenue yield changes once you build conversational channels. Look for how many more mentions/posts you get after starting blogger outreach. This is one of those "it depends" questions, and it starts with what kind of investment one means.
What social community do you find most valuable for business?
I find the communities vary. If I'm selling fashion, I might want to be big on YouTube or Flickr, for instance. If I'm looking to sell cars, I might find some great value in Twitter. If I'm pushing professional poker, Twitter's a great place, too. It depends on where and for what. There are great B2B conversations happening on Facebook and LinkedIn. It goes back to listening. Where will you find them?
How do social media and real-time search change the reputation management game? How can companies and brands control real-time spam?
Response to issues and concerns has to be much faster than it used to be. In the old days (pre-Twitter), responding within 24 hours was adequate. Nowadays, time to respond is down to a matter of a handful of hours (maybe as few as 4).
What tools and apps (paid or free) do you depend on daily for productivity and generally making your life better and easier?
Twitter, Facebook, Google Wave, WordPress for my blog, Radian6 for listening (disclosure: they're an occasional client), LinkedIn, and my Motorola  Droid. Living on a smartphone is almost a must these days for most of us.