A major scale is constructed of seven notes (within an octave) that relate to each other in a special way. The major scale is created by using a combination of whole-steps and half-steps. On guitar, a whole-step is 2 frets and a half-step is 1 fret. Below is a chart showing the relationships of the notes in a major scale using numbers for the notes and then how that works in a C Major scale. The notes are spaced (from low to high) W-W-H-W-W-W-H.
To create other major scales, we take the formula W-W-H-W-W-W-H and apply it to a note other than c. For example, let's take D Major. First, write down all of the notes from d up to d again, like so:
d e f g a b c d
Then, starting with d, we make sure that all of the notes fit our formula. So, first we check e to see if it is a whole-step away from d. It is, so we leave e alone. Next, we must check f. Normally, e and f are only a half-step apart, so we have to move the f a half-step higher. To do this, we sharp (#) the f to f#. Try finishing it yourself. Your answer should be:
d e f# g a b c# d
Still under construction...