By keeping such a checklist, you make sure that your tasks are written down all in one place so you do not forget anything important. And by prioritizing tasks, you plan the order in which you’ll do them, so that you can tell what needs your immediate attention, and what you can leave until later.
What you put on your checklist and how you use it will depend on your situation. For instance, if you’re in a sales-type role, a good way to motivate yourself is to keep your list relatively short, and aim to complete it every day.
But in you’re in an operational role, or if tasks are large or dependent on too many other people, then it may be better to focus on a longer-term checklist, and "chip away" at it day-by-day. Many people find it helpful to spend, say, 10 minutes at the end of the day, organizing tasks on their list for the next day.
Run through these checklists allocating priorities from A (very important, or very urgent) to F (unimportant, or not at all urgent). If too many tasks have a high priority, run through the list again and demote the less important ones. Once you have done this, rewrite the list in priority order.