There are four steps to learning the basic embouchure, they are:
This is the simple motion of bringing the lower lip over the lower teeth, with minimal or no extraneous movement of other facial muscles. Using unnecessary muscles shows itself in the form of dimples, lines, wrinkles, widening of the mouth, and bunching of the chin. These are all signs of unnecessary tension. By doing this step correctly you are creating the foundation for the next step.
Caution: Pushing the lower jaw forward into the lip can look very much like you are bringing the lip over the teeth, but by doing so, you are pushing your jaw out of it's natural plane which creates tension in the throat and puts the pressure point too far down the reed.
Bring the mouthpiece-neck or barrel combination to your mouth and place the reed on the lip with no change of Step 1: Set.
Practice this until you can do this 3 times in a row without change. The most common errors in this step are:
Blow air into the mouthpiece. Air sound only. You are not trying to get a sound. The pitch of the air should be low, and feel as if you are blowing warm air into the mouthpiece. Notice in the mirror if there is any change of facial expression, or deviation from steps one or two.
This should be done 3 times without change. If you notice any change you should go back to Step 1 and go through the steps.
While blowing add pressure of the lower jaw to the reed until a sound is produced. This is done with the use of the chewing muscles at the back of the jaw. It is the same motion as chewing or saying the letter "X". If the correct muscles are used there will be no change of your facial expression, as defined in Step 1. With some practice and careful attention you will begin to tell the difference between jaw pressure and lip pressure. Lip pressure makes the the sound "darker" and response slower.
These steps are to be done in exact sequence. Use the mirror to ascertain if you are maintaining the SET position as step 2, 3, and 4 are added.