I'm a big fan of to-do lists, but I've noticed something about them. If I have too few to-dos, I'm not really productive because I'm still trying to keep all my tasks in my head. If I have too many to-dos, I'm not really productive because I'm getting to far down in the weeds, and am unlikely to get to all of them.
If we chart to-dos on the X-axis and productivity on the Y-axis, this implies that to-do list productivity follows a bell curve, with a productivity peak around 5-7 tasks per day. The question is, how should you trim your list to the optimal length?
In my own life, I find that two things help reduce my to-do list.
The first is to establish habits. I don't bother putting things like "take the kids to karate class" or "cook dinner for the family" on my to-do list because I do it every week. The same applies to routines at work. Every startup operates on certain rhythms--daily deploys, weekly meetings. Try to make them into habits that don't require to-dos.
The second is to schedule a task on to my calendar, where I can rely on the calendar reminder to tell me what to do and when to do it. Once you schedule a task, you can stop thinking about it, and pick it up only when the time is right.
Whether you're using Asana, Trello, Basecamp, or (ahem) PBworks, managing the bell-curve of to-do list productivity can keep you and your startup on track.