Choose a bat for your needs. Fungo bats are lighter than regular baseball bats and come in metal and wood varieties. The idea is to find a bat that you can swing repeatedly without getting tired. In addition, pick one with a comfortable grip to avoid blisters.
Place your bat on your back shoulder and toss the baseball up with your front hand. Toss the ball high and far enough away from the body so you don't get jammed. Grab the handle with your free hand bringing the bat back a few inches. Hit fly balls at shoulder level, grounders at chest level and line drives at waist level.
See the baseball as being divided horizontally. During practice, aim at the lower half whenever you want to add some loft to your fly balls. Conversely, aim at the top of the baseball when hitting grounders.
Let the bat do all of the work and relax when hitting. If you are a coach, you know how tension can negatively influence performance. To be consistent, your swing should be confident and free of tension.
Perfect your swing. Hit each ball with purpose and visualize where you would like it to go or gather some players after practice for extra work. The more you hit, the better your fungos will be.