In Silicon Valley, it's not uncommon to hear all sorts of crazy tales about how to boost productivity -- from subsisting on  food supplement drinks to microdosing on LSD (really) to enhance cognitive functions.

But here's the thing: The world's most successful entrepreneurs know that there are much simpler ways to achieve maximum productivity.

Here are four productivity habits that have helped Jeff Bezos, Bill Gates, and Elon Musk rise to the top. And good news: These tricks are so simple, anyone can use them.

1. They prioritize email.

Bill Gates would use three monitors to stay on top of his inbox during his Microsoft days. One screen to display his incoming emails, another for the specific one he was reading, and a third one with either his desktop or browser displayed in case he needed to bring up a link or file.

SpaceX and Tesla founder Elon Musk prides himself in his deft use of email to get things done. "Wherever possible, I try to communicate asynchronously," he said on an on-screen interview with Mashable. "I'm really good at email."

Meanwhile, Jeff Bezos is notorious for forwarding single question mark emails to his team, in most cases about user complaints received on his public account, This practice allows the Amazon CEO to delegate issues to the appropriate manager without spending too much time on it.

2. They run no-nonsense meetings.

In his 1999 book Business @ the Speed of Thought, Bill Gates writes: "Good meetings are the result of good preparation." He says you should email documents and other data to people beforehand, so they can analyze ahead of the meeting. That way you will spend the meeting discussing the issue -- not presenting it.

Jeff Bezos uses a two-pizza rule to run effective meetings. He reportedly never organizes one where two pizzas couldn't feed the entire room. As for Elon Musk, a former employee revealed in Quora that he would ask employees point-blank why they're in a meeting if they haven't said anything. The rationale is that meetings are more productive when the attendees are limited to those who have a purpose for it -- either because they can provide information or implement a solution.

3. They sleep as many hours as needed.

The U.S. loses up to $411 billion in GDP a year due to insufficient sleep, according to a 2016 study conducted by the Rand Corporation, a nonprofit organization. Sleep deprivation affects your brain's ability to process information and in turn affects your productivity.

It is recommended that you sleep between seven and nine hours each day to be rested, but some sleep specialists, like Dr. Michael Breus, say that everybody's needs are a little different.

For example, Bill Gates says he needs seven hours per night, Jeff Bezos sleeps eight, and Elon Musk gets by with six or six and a half. They all agree, however, that they need sufficient sleep to be efficient during the workday. Figure out how many hours of rest your body needs and make sure you stick to it.       

4. They exercise.

You can count increased productivity among the many benefits of exercise. Studies have found that aerobic exercise, specifically, helps improve memory and learning skills. All three entrepreneurs -- Jeff Bezos, Elon Musk, and Bill Gates -- incorporate exercise in their routines. Bezos and Musk opt for weightlifting and cardio, and Gates spends time on the treadmill, sometimes watching some sort of educational content.