One white legal pad next to my desk, one pocket notebook and travel pen in my pocket. Have a thought or idea, write it down. Every Saturday I type all those notes into a running Google doc for the year and then put a check mark next to it on the paper.

I have a doc for every year. I regularly go back and read though them starting with the most current year and working back. If something is completed or used in a project I use the mark through function on that entry so it can still be read in case it could be helpful again but to signify that I've used it.

It's not a perfect system but it's helped me a ton.