Look at the key signature of the scale that you are practicing. In order to master scales, you need to know the key in which you're playing them. The key signature tells you how many sharps or flats the scale has. It can be found at the left side of the music line. Using a scale book as a reference will help you to know the various key signatures. For example, the C major scale does not have any sharps or flats. Therefore, the key signature will not have the symbols for either sharps or flats. The G major scale has one sharp -- and F# -- and that note will have a sharp over it in the key signature.
Play one octave of the scale. When mastering scales, you will want to be able to play at least three octaves without pausing between notes. To work up to this goal, play a single octave of the scale and hold each note for two or four beats. This will help you work on your transition between notes.
Play more than one octave of the scale. For example, after you feel comfortable playing one octave, you can play two octaves, and then three octaves. When you add the increasing amount of octaves to the scale, play each note separately and hold each note for two to four beats.
Play the scale with different rhythms. When mastering a scale, playing it with different rhythms and articulation will help you perfect it. For example, you can play the scale slurring each note, which means that you flow more smoothly from one note to the next as opposed to playing each note in a rigid, staccato fashion. Then, play the scale holding the first note for two beats, and then the next series of notes for one beat.