About a year ago, I took a useful course at Google called Getting Things Done, a system developed by David Allen. The instruction took hours, but I’ll sum it up for you in a few sentences:
Create lists based on location, device, or workspace, not based on project. For example, Keep a list of things you need to do at your work computer, a different list of things you need to do at home, etc. As soon as you know there’s something you need to do, add it to the list so you don’t have to worry about forgetting it. Once a week, spend a little time cleaning up your lists and checking off things that you’ve done.
It’s a good system. Read more about it if you’re interested.
One common implementation of this system was to use Gmail’s labels. You could send emails to yourself as list items, and then organize by label. To check off an item, you’d just remove the label. I used this for a while and it worked pretty well, because Gmail is ubiquitous. I always had access to it on my computer, and when I was out, I could get it on my iPhone and consult my “out” and “shopping” lists.
As you may have heard, Gmail recently added an experimental Tasks feature, which is simpler than using the workaround system of labels that people had created in the absence of Tasks. And, starting today, it’s now just as ubiquitous as Gmail if you use an iPhone or Android device. To take full advantage of it on an iPhone, I recommend creating a shortcut on your home screen as they suggest in the video. You’ll forget it’s happening in a browser.
Disclosure: I work for Google.