How do I learn a new opening? Often times, when I find myself going through the lines of a new opening, one that I would like to start using in my games I hit the concrete wall after a couple of days of studying it.

Due to the fact that this is new to me, I simply don't understand every strategic line behind it, and since I've never played it I don't know what to expect in a real game. So my question is:

During the first stage of leaning a new opening, just memorize the different possible variations?

Or 

Deep dive in the theory behind each move until you acquire a thorough comprehension of the tactical and strategical motifs?
The following suggestions will work for players in the 1600-2000 elo range. If you are above 2000, you probably already have better techniques than these. And if you are 1600 or below, tactics is arguably a lot more useful to learn.

Here's an assortment of things I used to try when I wanted to learn a opening. Note: I had access to Fritz and Chessbase and that helped.


Get a book (or a chess video) on the major ideas in the opening or variation that you are interested in.
This is fundamental. Watch it, or read it multiple times to absorb the themes.
Get hold of a bunch of games with your opening of interest. (Chessbase or Fritz makes this really easy). Sort them in different ways into smaller databases for your own reference.
Play through the games in various speeds. Click the steps fast, every few seconds, or very slow to absorb what's going on.
(Ideally, you want to focus on the games where your color of choice wins. That way you'll know the winning themes.)
I often learned by playing through games of players who were a 100-200 points above me, rather than from GM's. The reason was that my opponents would deviate from theory very early on, and I could see how players of strength comparable to me handled the positions.
Pay attention to the minor pieces and see which squares they usually occupy. Chessbase has a cool feature that plots the probability of a piece occupying each square in your opening of choice. I found that very useful.
Play through the games paying attention mainly to the pawn structure.
For me, it was usually enough to learn the first 10-12 moves and then the ideas. If you play the same opening enough, you can increase that to a few more moves.
I learned this technique from Silman's book. I'd print out a position (from the opening I was trying to get familiar with) and then stare at it and try to write down a very detailed evaluation of it. This was surprisingly difficult for me. I could come with a few basic points, and then I 'd go over someone's annotations and see that they could look much much deeper into the position. Doing this often can be quite beneficial.
I'd run my games through Fritz's analysis and watch in horror at the things both me and my opponent had missed. But I also learned not to miss those things the next time.
Keeping your own annotations is extremely useful. I'd write notes and keep adding to it as I learned more. Reading my own notes was often more helpful than reading the IM's and GM's who had much deeper knowledge.    


Hope that helps.