I've never believed in memorization.
I've always believed in learning.

I have a saying that's my own:
Memorizing for the low levels, learning for the high levels, and forgetting for the geniuses.

Let's say if you are trying to learn the opening lines for the Sicilian (as if life isn't short enough already), then I would actually recommend reading through the move sequence, play it out, and then write next to each move the purpose of that. Now, instead of learning the moves, learn the purpose of each move. Now you know what to do and what it actually means, when it is played. From then you should know what to do.