The following is the most effective method that allows players to memorize scales. You shouldn't learn a particular scale but the general configuration or, in other words, patterns. There is a table that shows the frets (n) where the root of the scales should be placed.
Try the Pentatonic and Diatonic page for a quick start. After you master the pentatonic/blues, major and minor scales, try “Toward Harmonic and Melodic” to step gradually from scale to scale.
In “Some Chords” you will find an easy method to learn most of the extensions of the major, dominant and minor chords. Remember the enharmony (for instance, b5 = #11; #5 = b13) and the “±7 congruence” (2 = 9; 4 = 11; 6 = 13).
In the following charts, you will find another method to play Major, Harmonic and Melodic Modes. For many guitarists, it's more comfortable to play three notes/string. Another advantage of this method is that it allows fast crossing from position to position.
3 by 3 Major Modes | 3 by 3 Harmonic Modes | 3 by 3 Melodic Modes
The modes you'll find inside the scale-charts:
Major Modes | Harmonic-Minor Modes | Melodic-Minor Modes
And here is the correspondence between the standard notation and the tablature:
Standard Notation and Tablature