Learn and practice the correct stance. Stand with knees bent and weight on the balls of the feet. Your body should be slightly forward. Your elbows should be in and your hands up in front of you both to block and to attack. Practice lowering your level and moving forward, again using the balls of the feet; this is the penetration step needed for takedowns.
Find a good wrestling partner. There is a saying in wrestling: "Champions come in pairs." You need someone of roughly similar weight who will work out hard, push you and make you push back.
Learn and practice two good takedowns--for instance, double leg and ankle pick. In a double leg, lower your level, take a penetrating step into your opponent, driving your head into his gut, while bringing your hands behind your opponent's knees or legs and pulling them in and up, thus knocking your opponent off his feet.
Drill the takedowns dozens of times each practice, sometimes with your opponent resisting you at 50 to 75 percent, so you can see how the move works, and sometimes practicing “live” at 100 percent.
Master the counters to “your” moves. For instance, a typical counter to a double leg is to sprawl, where your opponent will push his legs back away from you, while blocking your arms and pushing down on your head.
Learn and drill two good escapes for when you are in a defensive or “down“ position. A basic escape is a stand-up. Keep your elbows in, to make it harder for the top man to chop your arm and flatten you out. In a stand-up, you must quickly get hand control and come to your feet, driving your weight into your opponent. If you try to come up leaning forward, it will be easy for your opponent to force you back to the mat.
Practice the basic moves hundreds of times to gain “muscle memory,” which is when your body instinctively does the move correctly. You can drill without a partner, practicing placement of hands and limbs and quickness of movement.