5. Tackle your challenging tasks before lunch

All of us have different times of day when we feel most productive and energetic.

You can make the best use of your time by scheduling high-value work during your peak time, and low-energy work (like returning phone calls and checking email), during your "down" time.

You need to figure out when your brain works best and get heavy work done in those productive hours. 

These windows of 'brain time' cannot be wasted with meetings and chores that end up wasting your time.

We tend to ignore our energy levels when planning our work, but it's a major player in productivity. Everyone's energy spikes at different times—we each have our own built-in body clock called a circadian rhythm.

If you know you're most productive right before lunch, for instance, don't pla...