It’s standard productivity advice: Do your most important task during your most productive time. But even if you know when you work best, it’s not always easy to figure out what deserves your attention.

Prepping for a meeting with your CEO is probably more important than editing a memo on office fridge policies, but many tasks at work are more ambiguous. Given that time is limited, how do you establish priorities?

First, list everything you’ve got on your plate. Then, before you stop working each night, identify three to five items that must happen tomorrow. Here’s when something should earn a spot on this more limited, precious list:

In life, it’s always easy to shove off important–but not urgent–tasks. A colleague wants an email answered, so you do. You don’t have to work on that book proposal, so you don’t.

But keep in mind, people who accomplish great things in life prioritize those great ideas alongside mundane tasks. To be sure, you shouldn’t brainstorm how you’ll reform health care when your boss needs a document turned around in an hour.

If you put in an hour in your home office before commuting, or you get to the office early for some quiet time, then that can be a great slot for putting first things first.

Good managers strive to create a risk-free environment for people to ask what matters and what doesn’t. If you’re not sure what work should be done first, stop by your boss’s office and ask him or her to choose. You’re not bothering the boss. Assistance with prioritization is the core of management.