One of the efficiencies of the human brain is the way it filters short- and long- term memory. We can't remember everything, and even if we could, we can't access everything. In fact search is often more of a limitation than storage; we've all had the experience of having something "trigger" a memory, bringing back a whole bunch of long-forgotten (inaccessible) details.
These filters keep us from remembering high levels of detail for even small amounts of time. While you're in the middle of working on something you have a million details to hand, but as soon as you set it aside for a few days, the details fade. And if you come back to it weeks later, they're gone.
Those details are important. So people have evolved notebooks. Of course for the longest time notebooks were actual books in which notes were taken, but today they can be computer files, including ancillary data like photos and links. The first advice any young lab researcher gets is "keep a notebook". You're to log everything that you do, in the sequence that you do it, so that you can do it again (or avoid doing it again, as the case may be :) It's odd but I don't think the same advice is handed out to software engineers, yet it is just as vital, for all the same reasons.
When I start any project I immediately create a simple text file log, in which I record everything I do: date, time, and a simple description. Doesn't matter whether I'm creating something new, debugging a problem, or trying to learn something. In these days the log entries are often URLs of websites where I learned something, or which contained further instructions. Now that logs can be electronic, they can be searched easily - which makes them even more powerful.
This simple act of keeping a notebook is so valuable. As often as I tell people about it - as if I am telling them a great secret - they never do it. I'm telling you now, and if you try it, I promise you'll be a convert for life. But you're not going to try it, are you? Nope.
I'm not sure why people resist keeping a notebook of their work. There is extra effort involved, but it is trivial; honestly the time spent is in the noise, no matter how simple the project. And the value is so high! After even a couple of hours of digging into something, you're going to forget what you did and what you learned. After a couple of days, the gap will be huge. Yet people resist. I think there must be an extension of that efficiency I mentioned at the start, of filtering short- and long- term memory. We don't want to remember everything, because we know we can't.
Many many people use email as a sort of notebook, without even realizing it. For many people their inbox is a sort of to-do list, and their interactions with colleagues are a goldmine of information. Yet few people keep all their old email -as a sort of notebook - and even fewer have a good way to search it. For about fifteen years I've been keeping all my email (yes that is a lot), and for about eleven years I've used a little tool called X1 to search it. This is literally the third most used program on my computer (behind Outlook and Chrome). My colleagues know me as the guy who never forgets anything - a nice thing for which to be known - and X1 is the reason.
In the bad old days I used to take paper notes. Many of them. Every time I was in a meeting or presentation, I took notes. I filed these notes using a simple chronological system, and used an online text index to find them. So if I was in a meeting on 3/15/14 at 12:00, I might have made an entry that said: "1023 140315 1200 meeting with Spock to discuss Klingons and universe expansion". Then I'd write #1023 at the top of the paper notes, and put them in a file, just behind #1022 and ahead of #1024. Later I could at least find the notes, even if I couldn't search full-text search the details.
And now in the good new days since iPads (and Logitech keyboards) I take text notes. I use a little mobile app called Captio which captures typed text and sends it to me as an email. Subject line: "meeting with Spock to discuss Klingons". The email is sent, it gets saved forever, and indexed with X1 automatically. I can always find those notes and can full-text search anything which was discussed. My infinite notebook of notebooks.
Okay, I'm going to give this one last try. If you try to keep notebooks, I promise you'll like it. Well, I tried.