1. Always go straight up at least 50 feet above any obstacles before flying away, making sure to keep your eye on the Mavic (and not the screen) until fully clear when taking off or landing.
2. Take off and land with the green light facing you so all stick controls are intuitive.
3. Sports Mode: Never take off or land in sport mode, at least not in a tight area. Don't use sport mode when flying at very low altitude. Things happen too quickly.
4. Learn how to fly your Mavic home and land without the assistance of the RTH function.
5. Read the manual at least 2 times.
6. Start flying with a toy drone before risking a crash with the Mavic. Syma X8 or X5 are great starter drones to learn on.
7. Fly in a wide open field until comfortable.
8. Never fly inside.
9. Don't take off around objects or surfaces that may possibly affect your compass.
10. Be mindful of the wind. If in doubt, fly into the wind first.
11. Learn how to use the telemetry.
12. Follow a preflight checklist
The above are items right off the top of my head that I've found on this and other forums that pilots reported doing, or not doing, that ultimitly resulted in crashes.
And the most important one of all......
13. Learn from the mistakes others have made before they become your mistake.