If you've become a billionaire in your lifetime, you must be doing something right with your time and money. If you haven't, you may wonder, what are billionaires doing to make it happen?

As a member of the talent management and keynote speaking industry, I've spoken with a number of billionaires to find out their secrets. But out of all these conversations, I learned the most from Grant Cardone.

If you're not familiar with Cardone, he appeared on the show Undercover Billionaire, authored the New York Times bestseller If You're Not First, You're Last, and conducts popular seminars. The one thing that stuck out to me from all of his advice was not how to invest money or sell widgets. Instead, it was how to invest my time in learning.

In his talks, Cardone is proud to tell everyone the best piece of advice he got in life was from his mother. Mama Cardone told Grant: "The best investment you will ever make is in yourself." In his seminar, he calls this the 47 rule.

The 47 rule breaks down like this: If you invest 40 hours of your week in your business, then you should invest at least 7 hours a week on yourself--or one hour a day. One hour a day makes a difference over time.

For me, there are four basic ways to invest in yourself, as follows.

1. Read books.

In his talks, Cardone points out that successful billionaires like Warren Buffet and Bill Gates devote time each day to reading non-fiction books. If you're a reader, you could devote time each night after work or before bed reading in an area of interest to improve yourself. 

2. Take courses.

Sometimes you can't learn just from a book, so take a course. Companies like Pixar allow employees to take courses at work in whatever area they desire. For example, an accountant at Pixar can take a drawing course, or a Pixar artist can learn spreadsheets. Pixar realizes that learning in a different field can cross over and improve your performance or creativity. You could take one course online or at a local community college, averaging an hour a day.

3. Get coached.

Personally, I like private coaching. You could hire a life coach for personal stuff, a leadership coach for work, or a personal trainer to improve your fitness. The one-on-one nature of the coaching helps me learn better. If you can afford it, this is a great way to invest in yourself. Similar to the above, you could spend seven hours a week on your coached activities.

4. Schedule time for yourself.

Finally, you need to find that seven hours a week and hold yourself accountable to them. When you have work deadlines and family demands, you might find it difficult to set time aside to improve yourself. However, the busier you are the more important it is that you do schedule time for yourself.

Some good ways to find time could be setting aside time early in the morning when no one can interrupt you, staying up late at night after everyone else is asleep, or turning off all your electronic devices and closing the door during the workday. Whichever method you choose, stick to the schedule and you'll see results in no time.

Take it from a billionaire (or a billionaire's mom): The best thing you can invest in is yourself. I have used this 47 rule to improve my personal life and leadership and the results for my business have been astounding. We now have a better run business and I have improved personal relationships. And with these tips, so can you.