I learn’t this lesson the hard way nearly ten years ago when we first built the nutricherry site, we spent all our effort building a site that looked great, spending countless hours on user testing, to ensure the site worked properly.
We did all this only to find we had not worked out who was going to visit the site, and how they were going to find it. Needless to say I would not make this costly mistake again.
There are many, many platforms in the social media domain, and not all options will be good for every site. For example, some may want to put video content onto youtube and other video aggregators, where others may want to put professional contacts onto LinkedIN. Nearly everyone would want to have a facebook and twitter presence. Think carefully about who may want to link with you and which types of social media they may be using. Don’t forget that many businesses block most social media sites, so for professionals, this may severely limit what they have access to.
Further, I believe that the best strategy is to slowly build credibility by blogging, writing good content and making it known via social networks. Also, when appropriate using a PR company to get some extra exposure.