See this issue's cover story on social media and the law.

Facebook, Twitter, LinkedIn, MySpace, Tumblr, Flickr, Reddit, StumbleUpon, Digg. Social media websites, with their quirky names and various specialties, have proliferated in recent years. For most professionals and companies, a successful foray into the social media realm will involve creating profiles on “the big three”: Facebook, Twitter and LinkedIn.

Facebook: Facebook started in 2004 as a website exclusive to Harvard students and then, later, to college students across the country. In 2006, it was “unlocked,” and its popularity exploded. Though it began as a means for individuals to expand personal connections, it has since become a valuable business tool. Companies can create fan pages that Facebook users can “like.” Once a user “likes” a page, he or she will receive updates from that fan page in his or her newsfeed (a collection of Facebook activity from both friends and fan pages) and can interact with the company directly by writing on its “wall.”

Twitter: Twitter is a microblogging site that allows users to post brief updates—limited to 140 characters. While the site is criticized for promoting mindless narcissism among users, many public figures and companies have successfully leveraged Twitter as a means for interacting in real time with followers. Frequent (but not excessive) updates are key for building a loyal following.

LinkedIn: Billed as a professional social networking site, LinkedIn allows users to create an online resumé and to connect with both professional and personal contacts. The website also tells users when they have contacts in common with another user, facilitating the process of requesting an introduction for professional inquiries. The groups function on LinkedIn allows companies to create a hub where both employees and fans of the company can gather virtually to discuss relevant topics as a community.