A pencil and a piece of paper, or an organizer from Staples. :-D<p>If you're an Emacs user, org-mode is very powerful and quite useful as well. It's what I would be using, if I actually had a computer with me everywhere I go that could run it. <a href="http://orgmode.org/" rel="nofollow">http://orgmode.org/</a><p>If you aren't an emacs user, or are looking for an alternative, Taskwarrior is a quite popular CLI todo list management app, which has a similar (although not as extensive: org is frankly massive) featureset. It has a companion, Timewarrior, which is designed for tracking time and displaying reports. IIRC, this is an org feature as well. Both have significantly better mobile support than Org, so take that as you will. Either way, if you <i>are</i> going to support mobile, you have need to host the files yourself, or use dropbox. <a href="https://taskwarrior.org/" rel="nofollow">https://taskwarrior.org/</a><p>Pomodoro and GTD are both popular methodologies, which you can look into if you're interested in that sort of thing (I'm not, but I've heard good things about them both from people who are). They are applicable to just about any tool, including any of the above (yes, that means pencil and paper).<p>But ultimately, the only wrong way to organize yourself is one that doesn't work for you. So if anything I've listed works, and you want to use it, do. If it doesn't work, throw it away.<p>It doesn't matter what tools you use, just so long as they help you Get Shit Done (TM).