I try to put as much on paper or a digital equivalent of it as possible. My co-founder and I have habit of writing everything we hear, read about, or learn down so we can come back to it later. If it's for personal use - keep a word doc and just write down thoughts and discoveries, perhaps with links or references for you to re-read and re-visit later. For our business at http://Airdyme.io we keep a collection of spreadsheets pertaining to customer research, product development, fundraising and other activities. The more you can document the better. I believe even Airbnb's co-founder have mentioned a habit of writing down all kinds of crazy ideas on a simple notepad. You can watch that video here: https://vimeo.com/23275754