1. Start on any note. This note is called the "tonic" of the scale.
2. Move up one whole step to the second note of the scale.
3. Move up one half step to the third note of the scale.
4. Move up one whole step to the fourth note of the scale.
5. Move up one whole step to the fifth note of the scale.
6. Move up one half step to the sixth note of the scale.
7. Move up one whole step to the seventh note of the scale.
8. Move up one half step to the eighth note of the scale, which is the same as the tonic note an octave higher.
For example, to write the C major scale, start on the note C. The second note is D, the third note is E, the fourth note is F, the fifth note is G, the sixth note is A, the seventh note is B, and the eighth note is C, an octave higher.