Lastname, Firstname [or single username]. (handle). "First several words of Instagram post (if any)..." Instagram, Day month year posted, URL.
Username. (Year, Month Day). Enter facebook post here. [Facebook update]. Retrieved from http://facebook.com
Penguin, Oscar (2013, April 18). Root beer floats are in honor of National Library Week... [Facebook post]. Retrieved from http://facebook.com/openguin/posts/10154065808067067
Lastname, Firstname. "First several words of post..." Facebook, Day Month Year posted (if available), URL.
Lastname, Firstname. Facebook post. Month day, year posted. URL
Penguin, Oscar. Facebook post. April 18, 2013. http://facebook.com/openguin/posts/1015406580867067
@Username. "Full text of tweet." Twitter, Day month year posted, time posted, URL.
Username. "First several words of Tumblr post (if any, otherwise omit)..." Title of Tumblr blog, Day month year posted, time posted (if available), URL.