I don't really keep a traditional to-do list anymore. I tried GTD several times over the last 5 years and it's just too cumbersome (and having a huge to-do list is pretty daunting). I keep high-level project to-dos organized in Basecamp, project ideas are organized in soywiki, and any critical reminders are in Google Calendar (with alerts).

The real hack that I do though is every morning I take a post-it note and write down 3 things that I will finish that day. Then I stick it to my monitor and do the things. After that, I relax and play Starcraft 2 or work on personal projects.

Before I started using the post-it note, I would have a day or two where I was really productive, followed by several days of lackluster productivity. Now, by committing to fewer items per day but actually accomplishing them all, I'm way more productive overall, my clients are happier, and I'm actually making progress on my personal projects.