Why practice scales? Segovia gives us his cogent answer in the preface to his Diatonic Major and Minor Scales, published by Columbia Music Company:

The student who wishes to acquire a firm technique on the guitar should not neglect the patient study of scales. If he practices them two hours a day he will correct faulty hand positions, gradually increase the strength of the fingers, and prepare the joints for later speed studies. In one hour of scales may be condensed many hours of arduous exercises which are frequently futile. The practice of scales enables one to solve a greater number of technical problems in a shorter time than the study of any other exercise.

These words are from the greatest guitarist of our time and certainly one of its best technicians. (Anyone with any doubts about Segovia's technical prowess should listen to the Andres Segovia, The EMI Recordings 1927-39 on Angel Records to hear one of the most impressive techniques of this century.)

Jascha Heifetz, the great violinist, used to audition prospective students simply by listening to them play nothing but scales! Heifetz believes the scale is the most important phase of technique. "The foundation of everything is the scale." If you need any more encouragement to practice scales, read the words of any great musician about the development of technique.

How one practices scales depends on one's objectives. For most students in the first few years of study, it is advisable to practice them very slowly with the objective of developing correct hand positions, finger movements, good tone quality, and particularly hand coordination. Hand coordination is an often neglected problem. A lack of coordination between the hands leads to very unmusical playing: choppiness, unwanted glissando, fingernail noises, and disjointed, uneven shifts.

I would advise practicing your scales as Segovia has indicated in his booklet of scales. Use im, mi, ma, am, ia, ai, and imam. Although Segovia only recommends using rest stroke, I would also practice with free stroke. Practicing in triplets (with a heavy accent on the first note of each triplet) is very helpful in playing evenly, especially at shifts:
Many students have difficulty developing right hand alternation speed. For this, practice one or more of the following formulas:

To work solely on scale velocity (begin this only after mastering correct hand positions, finger movements, hand coordination, etc.) I recommend working on chromatic scales and especially scale passages from actual pieces. Passages from the first movement of Rodrigo's Concierto de Aranjuez are especially valuable. I say this for the following reason. Unlike a pianist, who can use virtually the same fingering for a scale in many different pieces, the guitarist, because of the nature of his instrument, must use different fingerings for a scale depending upon the context in which it occurs. Therefore it makes more sense, and will save the player time in working on scale velocity, to work on scales with fingerings used in actual pieces rather than mastering one particular set of fingerings which cannot always be used in the repertoire. Now remember I am talking about developing scale velocity here. I strongly recommend scales with set fingerings, such as the Segovia scales, for working on other prev ioned aspects of scale technique.

Opinions on whether one should devote a lot of time to scale practice in one's advanced stages of technical development are divided. Violinists Vehudi Menuhin and Joseph Szigeti feel that after one has developed a sound technical foundation, the benefit to be derived from scale practice is limited. Mischa Elman and JaschaHeifetz, on the other hand, believe scales should be practiced constantly, all through one's life. At one time Heifetz stated that a student should devote three-fourths of his practice time to scales! I personally still practice scales a half-hour each day. I find a certain comfort in their practice; a feeling of security is generated, as well as a high sense of orderliness in technique.

Make of this what you will. Every artist has their personal practice routine and recommendations on how much time to spend on technical work. But I believe there is no denying the importance, nay, necessity of assiduous scale practice in the early through intermediate stages of a student's artistic development.

Click here for a related article