As a relatively unskilled player, I am not, at this point, capable of memorizing numerous opening variations. The vast diversity and eccentricity of openings utilized by my opponents here at chess.com precludes me from ever memorizing everything that I'll see. Beyond that, my attled brain is incapable of memorizing the Ruy Lopez opening; never mind the Queen's Gambit Declined.
Instead, I try to focus on guiding principles: control the center, trade a flanking pawn for a center pawn when feasible, develop bishops and knights ASAP, and position, position, position. Many positions I encounter are common amongst a vast array of openings. Bishop, knight, and pawn location will often transpose into a common line, despite my ignorance and accidental encounter with the opening.
In an attempt to better master the game of chess, I often find myself reviewing the games I've won and lost. To help offset my personal ignorance, I have my power of the internet. One of my most commonly used bookmarks in Firefox leads to an ECO help page, which lists each ECO code, along with the moves that make the opening unique. Ctrl-F to search, and I enter the opening moves from my own game: "1 e4 e5 2 Nf3 Nc6 3 Bc4 Nf6 4 d4 ..." Unbeknownst to me, I had just encountered the Two Knights Defense C55.
Armed with this knowledge, I turn to another oft used bookmark, an online database of chess games played throughout history. Presented with a search page, I enter the ECO C55. Among other gems, I discover that Paul Morphy utilized this opening to defeat Jules Arnous De Riviere in Paris, 1863.
For some strange reason, I take enjoyment from going over old chess games. It feels as if I'm watching an old sporting event on TV. I know who is going to win, but watching the masterful way they go about it can be exhilerating, even 147 years later.
In addition to the entertainment value is a learning opportunity, which I would reccomend to anyone who is looking to improve their game. Study the positions that the masters chose for their pieces. Ask yourself why there? Understand the motivations behind the movements, and you can establish some guiding principles of your own. With luck, you'll stumble into some winning positions and recognize them from the games you've seen.