I've maintained a personal one for over 20 years of different designs and architectures etc. Sometimes I'll save code snips when they were particularly creative, but pretty rare. In general it is more for me to reference designs and help me be creative on solving new problems. One of the interesting things is looking back and seeing designs/solutions that were popular 20 years ago are still going strong, or in some cases are being sold under a new name as the greatest thing ever to exist and being totally new. I think that is fair of any industry though, so it isn't knocking anyone/thing, just kinda fun to see.
A lot of my notes are about particularly interesting problems or things that didn't work as much as things that did. This way I can try and not repeat mistakes or at least see why it went wrong and what might be different now. BTW I do this using an everyday spiral notebook (5 subject) to hand write things down and then over time I transfer them into a 3 ring binder I keep. I also keep the old notebooks which I usually date and write what I was doing then. The 3 ring binder is where I keep the stuff that seems more important and isn't just my quick notes, it will be sketched designs, written notes as well as the occasional code snip printed. I know I am evil but I also keep some important pdf's I have printed in there because frankly it is easier to keep track of then the electronic document over 20 years.
I also keep notes for each company I work at/with, generally I do those in some repository for the company (it is the companies not mine). This is nice because it gives others, not just me, some historical information on why things are and what we were discussing or other thoughts we might have had while doing design discussions. Today I use Quip for a lot of that for company specific notes, and honestly it helps for on-boarding too.
A few years back I started using OneNote as well for my personal notes, this has worked pretty well but I still handwrite a ton of stuff because I find people banging on a keyboard in a meeting hiding behind their laptop to be rude & distracting, so I won't do it. But I have been moving even some of my handwritten stuff into OneNote and/or Apple Notes, which I started playing with recently as well. What I like about both of them is they sync to multiple devices so I don't have to go digging as much.
A lot of my notes are about particularly interesting problems or things that didn't work as much as things that did. This way I can try and not repeat mistakes or at least see why it went wrong and what might be different now. BTW I do this using an everyday spiral notebook (5 subject) to hand write things down and then over time I transfer them into a 3 ring binder I keep. I also keep the old notebooks which I usually date and write what I was doing then. The 3 ring binder is where I keep the stuff that seems more important and isn't just my quick notes, it will be sketched designs, written notes as well as the occasional code snip printed. I know I am evil but I also keep some important pdf's I have printed in there because frankly it is easier to keep track of then the electronic document over 20 years.
I also keep notes for each company I work at/with, generally I do those in some repository for the company (it is the companies not mine). This is nice because it gives others, not just me, some historical information on why things are and what we were discussing or other thoughts we might have had while doing design discussions. Today I use Quip for a lot of that for company specific notes, and honestly it helps for on-boarding too.
A few years back I started using OneNote as well for my personal notes, this has worked pretty well but I still handwrite a ton of stuff because I find people banging on a keyboard in a meeting hiding behind their laptop to be rude & distracting, so I won't do it. But I have been moving even some of my handwritten stuff into OneNote and/or Apple Notes, which I started playing with recently as well. What I like about both of them is they sync to multiple devices so I don't have to go digging as much.