One thing I've been doing for technical books and papers recently is focusing on coming back to material regularly, especially if it's something I don't see frequently. I've used Anki in the past for this, but I actually ended up making my own simple spaced-repetition based app to handle the "when should I review this material" question.<p>Combined with outlines I make for myself for the material, this means I can have a pretty regular review to keep things fresh in my mind. If things are a little too rusty, I can either review the source material or review it sooner the next time.
Read something. Close the book. Try to do the thing described. Struggle. Get it right. Repeat until you can't get it wrong. Move on to the next thing.<p>Say you're reading a book on programming with some examples to do something such as opening a file and reading it in language X. You read the code example. You close the book, you try to do it from memory. You struggle a bit until you get it right. You start over from a clean slate until you do it casually. Then move on to the next one.<p>A bad way to do it would be to read the example, say "Oh, I get it" and move on to the next example. Test yourself by closing the book.<p>This works for many things. You're watching a video about how to make a knot? Watch the video, then pause it, get a piece of thread/wire/cord, and <i>do it</i>. You most often than not will figure out that you <i>thought you got it but you didn't</i>.<p>A maths/physics/engineering book? Same thing. Read the problem statement. Go over it/try and solve it.<p>Thinking you "got it" is a hypothesis. Aggressively and systematically test hypotheses.
I found the best way to retain info, although it’s a lot of work, is to write down questions for myself as I read. Usually a bunch of fill-in-the-blank style questions.
I don’t write down the answers as I’m reading though I sometimes put page numbers where the answers can be found. I wait for a least a couple hours after I’ve finished reading, and up to a day, then go back and answer the questions I’ve put in my notes.<p>I’ve found this is by far the best way to force myself to engage and retain info. I’ll also occasionally copy over critical notes to something permanent like Notion or Roam, just to be sure I have a quick reference several years down the line. It’s time consuming, but probably still a time win compared to using multiple sources to learn a single topic.
I have a largish white board (thanks home office) on which I summarize a (sub)section of a book / online course in my own handwriting / symbols / diagrams after reading / watching it first and doing the summarizing on a second run (after which I take a photo and save it to a doc on the topic).<p>This method has helped me commit quite a lot of conceptual information into long term memory - but - it is time consuming.<p>If I ever need to refresh my memory on a topic, I pull up the photo and redraw it - sometimes adding or changing things a bit - then take photo again. Rinse and repeat.
I highlight sentences that summarises different ideas of the book. Afterwards, I create flash card for each highlight to review these them regularly.<p>Currently using readwise with highlights exported from kindle (when possible). I also use Anki for all other flashcards.