Don't: Forget to keep your social pages and status updates current. I'd get on it right away if I were managing the President's PR crew, as having an outdated profile in a special interest group niche could give one the impression that you're not paying attention anymore to that constituency and its needs.
Proactively seek out the free listings first. The ones that are selling ads will seek you out and beg you to spend. Personally, I would hire a competent social media/marketing consultant first and foremost before I paid for advertising.
Jumpin' Goat's 6,000 loyal followers even lead to mainstream media coverage on AOL small business and ABC News. http://bit.ly/9DgHdF.