This is a great infographic that summarizes what each social network is about using as an example (and my favorite), donuts.
Some sites are about eating donuts (twitter), reviewing (yelp, foursquare), the visual side (instagram, youtube), recipes (pinterest), history (quora), and more.
When you think about how to portray your business information, just look at this graphic and figure out what is your ‘donut’.
And don’t we all love donuts?!