How to memorize opening theories

I am declaring this respectfully. Please do not say anything that are similar to:
1) "You don't need to memorize opening theory"
2) "At ... rating, you don't need to memorize opening theory and long opening lines to prep against your opponent"
3) "Memorization is not effective or even useless"

This is a formal forum post seeking legitimate advices, not jokes that waste everyone's time. If you have helpful advice, post it. The people who need it would find it helpful. For the people who aren't interested in this topic or want to argue about the justifications behind memorizing such things, it is for another forum post. So, hope you guys provide insights for everyone!

Remember, we are only discussing the how, not why, nor who or when.

I think that this quote gives the basic idea for learning about a specific opening:
"... The way I suggest you study this book is to play through the main games once, relatively quickly, and then start playing the variation in actual games. Playing an opening in real games is of vital importance - without this kind of live practice it is impossible to get a 'feel' for the kind of game it leads to. There is time enough later for involvement with the details, after playing your games it is good to look up the line. ..." - GM Nigel Davies (2005)
In a nutshell, pick up what you can from quickly playing over some games (skipping a lot of the details). Then use your own games as a guide for where to learn more. I once wasted a lot of time, reading about the position after 1 d4 d5 2 c4 c6 3 Nf3 Nf6 4 Nc3 dxc4 5 a4 Bf5 6 e3 e6 7 Bxc4 Bb4 8 O-O O-O 9 Qe2, only to realize (eventually) that the position never arose in any of my games.
Here are some more quotes on learning about openings:
"... For beginning players, [the book, Discovering Chess Openings by GM Emms,] will offer an opportunity to start out on the right foot and really get a feel for what is happening on the board. ..." - FM Carsten Hansen (2006)
web.archive.org/web/20140627114655/https://www.chesscafe.com/text/hansen91.pdf
www.amazon.com/Discovering-Chess-Openings-Building-Principles/dp/1857444191?asin=1857444191&revisionId=&format=4&depth=1
"... Overall, I would advise most players to stick to a fairly limited range of openings, and not to worry about learning too much by heart. ... the average player only needs to know a limited amount about the openings he plays. Providing he understands the main aims of the opening, a few typical plans and a handful of basic variations, that is enough. ..." - FM Steve Giddins (2008)
"... Read many annotated game collections ... By looking at entire games, the aspiring player learns about openings, middlegames, and endgames all at one fell swoop. Playing through annotated games spurs improvement as the reader learns how good players consistently handle common positions and problems. ..." - NM Dan Heisman (2007)
web.archive.org/web/20140627062646/https://www.chesscafe.com/text/heisman81.pdf
"... As is the wont with modern opening works, these books usually centre their recommended variations around an instructive and/or entertaining game, without great depth but with sufficient detail to show the main branches and explain basic ideas. This is absolutely legitimate ..." - IM John Watson (2012)
web.archive.org/web/20140627015516/http://www.chesscafe.com/text/hansen163.pdf
"... I am not a big fan of weaker players memorizing lots of opening lines they will never play. However, it is quite a different issue to spend a small amount of time learning how to play your openings a little better each time they occur. A long journey begins with a single step. ..." - NM Dan Heisman (2005)
web.archive.org/web/20140627023809/http://www.chesscafe.com/text/heisman50.pdf

Why do you want to memorize theory anyway? Unless you are a chess pro your opponents won't play much theory anyway. Like if you memorize 25 moves of Najdorf theory they will probably play some random side variation.

anki is a free app for spaced repetition that supports chess moves.

I guess there are at least 2 parts to learning, understanding and memorisation. You need both. Don't just memorise moves, understand why the move is recommended and memorise both the move and the why.

What I do is to annotate lots [100+] full games in the opening: first my recollection and ideas. Then I look it up in a book and add then I turn on computer analysis and add.

I also then 1. write my own little pamphlet of the main lines I want to play and I make a test position of the critical moves that still dont seem intuitive and go thru them periodically.

I also play thru as many annotated GM games in it as I can find, trying to anaylze stuff like ''Why not this?''. For one that I play it been about 500 games.

Seems like overkill.

Now if I want to review I go thru the short pamphlet and do the test positions.
Bill

I also use Chessable and their spaced repetition and as a beginner I would start with a complete repertoire, meaning in one course you get lines against "all"/the common starting moves.

After every chapter in the Chessable course I transcribe all the moves and every variation to Chessbase and go over it, adding comments and highlights for important squares and what the game plan should be. When I don't understand a move or don't understand why my opponent cannot play this or that I think for myself/ask the engine and add that variation. Finally I feed the whole file in ChessTempo's opening trainer, which also works with spaced repetition but now every variation and more is covered compared to the Chessable course.

When I feel somewhat solid about my moves, I start playing them. After each game I check against my opening repertoire and when my opponent played something different, which stumped me, this variation gets added.

Rinse and repeat.

Chessable, which I don't use.
studyopenings.com is what I use, but haven't really had the time to assimilate anything
chessbase if you want your opening repertoire to be more private.

Personally, my question to you (since you are a better rated player than me) and to the lichess community), is HOW to study openings, in order to memorize them?
My understanding is that w/o having plenty of data on the middlegame (strategic concepts, pawn structure, tactical motifs) of one particular opening, memorizing mainlines will help one to penalize opening blunders and to develop efficiently, from a theoretical pov, but that's pretty much it. Thanks

After the memorizable typical open to your opening common sense moves are either category developing to castle, developing to strengthen center, develop to defend a square, take space........ Just remember that.

Then go into your middlegame strat or typical plans what's the center like yaddi this yaddi ya