THE ALMIGHTY MAJOR SCALE:
The major scale is a most know for all guitarrists. With it, the melodic parts are usually created and the runs on it are usually cool.
The major scale has 7 forms on the fretboard that start on each degree. These same patterns create the modes.
The first you should do is as memorizing the patterns:
The example below is the the major scale in all the fretboard in the key of G: