I've discovered that my brain is fantastic at storing useless information that I can call up without any notice or reason. When I try to do the same thing with knowledge that is important to me, my brain decides that it doesn't want to work.
So, like when I was in school, I take notes whenever I need to remember something important and I'm afraid that I'll forget it. I'm doing this more often with blog posts, too. I don't scribble anything down when I get post ideas, but with this post (and several others) I simply logged in to blogger, jotted a few words down, and then saved the post as a draft.
When I'm working on a book, especially in the early stages, I like to daydream to put together the plot, the character interactions, and many of the other parts of a book that are usually handled in the planning and outlining stage. I often have time for this on long car-rides or while I'm working since my brain is occupied with a menial task that requires little concentration. (And believe me, when I need to focus on something important, I stop thinking about my book and focus on my job!) I found that, unlike when I was 13, I forget these ideas quite easily. So I'm taking more notes and I puzzle out my plots.
My point, I guess, is that note-taking, while tedious and capable of making you feel old, is very useful, and even helpful. Sometimes, especially when you're playing RPGs, it'll save your life!