How to learn openings effectively?

I couldn't find a discussion of this matter, but please tell me if there is one.  

I am returning to the game after many years, and have a severe case of chess fever.  I am about to join a local club, where I will play in tournaments.  I have the time and motivation for study and practice, and have a pretty good idea how to study tactics, endgame, strategy, etc.  What I don't know is the best way to study openings.  I have always played openings spontaneously, but that's not going to work anymore now that I'm serious about the game.  

So here's my question.  What are the most effective methods, and overall strategy, for developing a repertoire of openings?  Ok, so there's chess mentor.  And I expect some will say, "you just have to learn by trial and error in your actual games."  All true, but I want to find the most effect materials and methods so that I can get comfortable as soon as possible.

Thanks for your help!

First question is ask if you are more comfortable in open or closed game settings. Then find a general opening book to explore openings that lead to these types of mid game positions. If you have played lots of games already, then many of these positions will be familiar to you. That should be your starting point.

Can you name a good "general opening book"?

I'm looking for this aswell.

Standard Chess Openings by Eric Schiller. It has most of the standard openings being used in tournament play. to accompany that you can also download the Caxton opening DB that on this site, which has pretty much every opening used in existence. I use it as a way of classyfing my pgn files.