Heading is used to play high balls, clearing, passing, or attacking. In the first exercise, we have the players sitting down toe-to-toe. With a self-toss, we use just our upper body to strike the ball to our partner. When each of us is successful, we take a step back, and we repeat the exercise. We continue the exercise until we've reached the distance where we no longer can succeed. You can do it as a contest. As soon as one player can't reach the partner, then that partner gets a point.
The second phase, the players move to their knees. Again, we use a self-toss. We arch backwards, and we drive forward so we land on our hands. Again, you can use this as a contest, where after each successful head you take a step back. In this exercise, there's no energy coming from the surface of the ball, so all of the force comes from the player.
In the third exercise, the players are on their feet. They still use a self-toss, and they drive from their feet through their waist, using their legs, and all the way through following through with their neck. Again, you can use this as a competition, where after each successful toss you take a step back.
In the fourth exercise, we add a third player, and now we're changing direction of the ball. We're heading the ball on an angle sideways. After a few laps around the triangle, we change direction so that we're heading the other way.
Practice proper technique to keep you safe, keeping your heading-specific practices less than 30 minutes.