How to learn an opening I'm a ~2100 Elo rated player at the moment, and lately I've been wondering about the best general way of learning openings, and eventually mastering them in some sense. Note that this question is not in the same spirit as the question What's a good way to learn opening theory?, already answered earlier.
My question is a general question about methods, in a few parts:


What are some good methods to pick up an opening you've never played before? Are there any differences in approach if the opening is somewhat familiar, or completely new (think going from the French to the e6 Sicilian as Black vs. going from the French to the Pirc as Black)?

If you've played an opening for a while, and you're not getting good results with the opening, how can you determine if the poor results depend on you not knowing enough theory/ideas or if it's more fundamental, like the opening not suiting your style?

How do you determine if an opening book/DVD/[Whatever thing that costs money] will help your understanding of an opening before buying it? It's not very fun to buy something that won't be very useful in the long run.

Is it even necessary to get books on openings to learn them? How much more difficult is it really to learn openings without books, and what are necessary things to consider if you're trying to learn an opening by studying games in a big database? How much does this depend on player level?

How much time is it reasonable to assume that it takes to master an opening on average? How much does this depend on the type of opening? Take, for example, the London system as White vs. the King's Indian Defence as Black, where the first is a &quot;system opening&quot; that's not very sharp, and the latter is incredibly sharp and complicated.



I don't think that this is the type of question that can have only one good answer, and I would hope to see different people mentioning their methods of choice for learning openings. It's not easy to learn to play an opening well, if you don't know what's necessary to learn. I mean, otherwise every grandmaster would be as good on the Black side of the Najdorf Sicilian as MVL.
Try to understand the key idea behind the opening, and try to relate each of the main moves to it. If you can't do this, you don't understand the opening.
First test the new opening by playing it against players weaker than you (in your case, &lt;2000). If you are getting bad results, it means that the opening doesn't suit your style. Then test the new opening against players stronger than you (>2200). If you are winning more games that usual, the opening is "value added;" otherwise it's "back to the drawing board.
If I buy a book or DVD, it's because something I've seen makes a "lightbulb" go off in my head. If I don't have this "aha" moment, I don't buy the item.
The greater your strength, the less benefit you will receive from books, and the more benefit from your own study. If you are the "smartest kid in class," you won't benefit much from reading others' papers.
Depending on the opening, mastery could take from a few months to years. Some GMs spend a lifetime trying to understand one opening.