Here's a link to a bunch of blog posts written as a series as a Social Media Start Kit. It covers Twitter, LinkedIn, Facebook as well as software and hardware.
Some of it is very basic stuff, but for the complete newbie or if you find yourself in the position of needing to explain it to a client, then it's a great read. You can also download it as an e-book.
http://altitudebranding.com/category/smstarterkit/