The Blues Scale
The Blues scale consists of I bIII* IV V bVII** notes of the major scale. Thus the A Blues scale is derived:
These notes can be arranged into patterns for simplification of learning and playing. The most common of these patterns is called pattern 1, which is outlined here:
This pattern is used by every Rock lead guitarist and you should memorize it and practice it every day.
Pattern one can be used for improvising against the Blues progression in the key of A. Record yourself playing a 12 bar in A, using any rhythm you like. Now play through pattern one (playing one note per beat) and observe how the notes blend in with the 12 bar chords. Notice that any note from pattern one can be played against any chord in the progression.
This Blues pattern can be used to improvise against any Blues pattern in the key of A. The Blues scale can also include the flattened 5th note ( bV ).
* bIII indicates that the 3rd note of the scale is flattened.
** bVII indicates that the 7th note of the scale is flattened.
Triplets
Now that you know what notes to play, you have to learn how to play them. This will involve learning, amongst other things, various techniques that all lead guitarists use. One of the most common of these techniques is the use of triplets, which can be defined as three evenly spaced notes played in one beat (indicated thus 
*). They should be played with an accent on the first of each three (i.e., accent each note that falls on the beat, creating a "waltz" feel.
Blues Scale - Triplets
(To be played against the 12 Bar Blues progression). Each note of pattern one can be numbered as such:
Triplets can be played in the following order.
Be sure to follow the correct pick motion (alternate picking) and count 1+a,2+a,3+a,4+a, accenting the first note of each three (indicated by the arrowhead >).
Also play the major scale using triplets.
To conclude this lesson, try some improvising by playing various note combinations of pattern one against your recording of the 12 Bar Blues in A. Play slowly and carefully at first, since accuracy is more important than speed at this stage.
