Finding time to enjoy life is becoming harder and harder. As the average work week lengthens, leisure time drops.

Yet some of the world's busiest people are able to develop rewarding careers and also make time for family and leisure activities. Here is their best advice, plus that of time-management experts.

1. Use your peak hours wisely.

When is the best time to undertake important tasks? Normal body temperature can vary as much as 1.6 degrees Celsius during the day. These patterns correlate with the rise and fall of your working efficiency, mental alertness and feeling of well-being.

Simply lounging in bed in the morning can rob you of productive time. "Long ago I learned a trick that saves me 20 to 50 minutes a day," one busy man told me. "I simply get out of bed when I wake up. Lingering only delays the inevitable, and you aren't getting any real rest anyway."

People tend to be most alert in late morning and mid-evening. Afternoon brings an increase in sleepiness, with a "trough" in efficiency occurring around 2 or 3 p.m. After body temperature peaks between 6 and 8 p.m., many people experience a decrease in alertness.

Use your high-efficiency hours to tackle difficult jobs or engage in creative thinking. For low-efficiency times, concentrate on reading the newspaper, cleaning up or sorting your mail. By adapting to your mental condition, you can accomplish more in less time.

2. Make a plan.

Would you drive to an unfamiliar destination without a road map? Time-management experts agree that the most productive minutes of your day are those devoted to planning ahead. Just 20 minutes of organizing can save an hour of extra remembering what must be done. "Don't try to carry your life around in your head," says an expert. "Write things down so you can free your brain for more creative pursuits."

Make a to-do list every day. If you have fewer than ten items, use numbers to prioritize your list. If you have more, group the most urgent task under "A", less important under "B" and least vital under "C", or rank items with different colored highlighters.

In less than ten minutes, a New York City attorney, a mother of four, lists all household tasks to be completed each day. Through good organization, she is able to manage her family and professional responsibilities, and also stay involved in church activities and a university board of trustees—and do everything well.