Remember that the singer’s mouth and lips must always be mobile and relaxed, so that they can adjust themselves to the change called for in the pronunciation of words. Correct tone placement, however, must go on, regardless of the change of the shape of the mouth or lips, as the tone is formed behind the front of the face, and without any help from it.
To assure lip relaxation and to avoid the difficulties that arise when a beginning student starts on repertoire, present simple vocalizes and exercises from the very first, using easily pronounced words such as "Caro Mio Ben" or "Love is Mine" to the very simplest of arpeggios.

Be sure that all voice types under your supervision practice scales. Scales achieve and maintain requisite vocal flexibility, and are just as necessary for low voices as high ones. The scale, however, should be attempted only by the advanced student who is sure of voice placement so that the tones will not be slurred. A few difficult vocalizes should be practiced every day to promote vocal agility.

See to it that beginning students do not form bad vocal habits between lessons. It is often best to advise abstinence from practice for the first few weeks that a new student is under one’s guidance. It is advisable for such a student to have as many lessons as possible per week until the correct method of voice placement is definitely established in his mind. When this is accomplished, the student will be able to practice alone without any harmful consequences. The experienced singer seldom heeds such advice, although it has been my experience that he needs it as much as the novice.