Since this site is a collection of technical notes, it's helpful to step back and look at why taking notes is a good habit, and look at one approach to taking notes easily.
I originally thought keeping backups was the most important topic to describe. As I was writing those notes, I realized that many of the original circumstances making that so important have changed. With the advent of 'the cloud', many of us are no longer keeping important personal information on a single machine with a single hard drive. (If you are, maybe skip ahead.) With that single point of failure fading from the picture, it seems the situation has changed. I was brought back to this topic: the importance of learning to learn.
With time comes change. Some would argue that we're actually at a point in time when the rate of change itself is changing. Regardless of rate, we know change will come. To adapt to change, we must learn about the current state of affairs. Then, once things change again, we'll need to learn about *that* new situation. It's an endless cycle. Therefore, it makes sense to stop and evaluate the way you learn every now and again.
Can you make your own learning process better? We all learn differently. It's an important question to spend some time with.
That said, here's what I've found works well for me: take good notes. I like to keep my notes digital so I can (hopefully) find them again later when I need them. I also like to keep my notes in plain text so that I'm not locked to one proprietary program or platform. I have written an open sourced library (Moments) to help sort and organize those notes. Recently, I also started a draft of a web application to help create moments. It's available thanks to google app engine at http://present-moment.appspot.com.
There is also some documentation and examples (Context) to help explain the process and format. For now (2010.10.07 20:02:11), Context is published using a version control system, which is not immediately intuitive for most. Soon I hope to make those more browser friendly via contextiskey.org. Stay tuned.
If that process seems too complex or too cryptic, the simple version is this: keep notes in a simple format that makes sense to you. Review and revise those notes as times change.
If notes aren't your thing, remember to step back every now and again and consider how you do what you do.
I also find it helpful to take a deep breath whenever I can. Happy trails.