Newbies: Where to start?

Hey everyone, 

I'm new to chess.com, and more importantly, new to anything more than casual chess. I've never really been in a club, only played with friends, so I know very little to nothing of chess theory.

So my question is: where should I start learning, and where do I go from there? Should I study and learn all or many of the openings and book lines, should I study general tactics? Chess is a complex and beautiful game, and I don't know where to begin.

Suggested reading material is welcome. I did recently buy Graham Burgess' Chess: Tactics and Strategy, and am working my way through it.

First thing you have to learn is to look at diagrams and ask yourself : what would I play here if I was white ? If I was black...

I would suggest learning all the basic principles, such as castle early and centralize the knights.

When you get better, you learn that these principles are useless, but...