A good task list is:

• Unambiguous and explicit. Each project and action should pass the Nike test. If you delegated this to someone else, could they "just do it"?
• Broken down into the smallest practical steps. Here's why:
  • There's a low cognitive hurdle to getting started.
  • It helps to prevent procrastination.
  • It makes it easy to batch tasks like email.
  • It makes it easier to delegate, particularly if your tasks pass the Nike test.
  • It's easy to pick up where you left off when you get interrupted.
  • You can make the most of the odd gaps of time that we all get every day.
• Complete

• Reviewed frequently to keep it up-to-date. To-do lists go off like dairy at the back of your fridge. After a few days, they start to smell. After a couple of weeks, you don't want to go anywhere near it. After a month you're holding the thing at arm's length as you throw it in the rubbish.

• A good task list doesn't overwhelm. It should give you a game that you can win. If you can't expect to make progress on something in the next week take the project off your list. Put it on hold, move it to a different list for projects to come back to or delete it altogether. But don't have a to-do list that keeps getting longer and longer.

• Organised so it's easy to find what you want when you want it and you're not distracted by tasks that you can't do.

• Easy to update.

• Give you a significant pay-off. If you don't get a good return on the effort that it takes to maintain your list then it's time for an overhaul. You can start by checking it against each of these points.

• Make it easier to say no. It's easier and more comfortable to say no once you can see the full extent of what you've already taken on. If you’ve already committed to more than you can do, what's going to make way for this new thing that's appeared?

• Something you rely on as much as your diary and your contacts app.
• Frees up your cognitive energy to focus on what you want to do, not trying to remember what you have to do.

This isn't a complete list but if your task list checks all (or even most) of these boxes then it should be in good shape.