There are many scales that are used when playing the blues and the Blues Scale is best used when combining it with other scales such as the Major scale, the Mixolydian scale and the Dorian scale when improvising over blues progressions. One of the great things about the blues scale is that is is not limited to the blues! It is used in Blues Rock, Rock, Reggae, Funk, and even Metal. I have played many Metallica solos using this scale.
The blues scale is really just the pentatonic minor scale with one additional note. In the TAB below we see the A minor pentatonic scale then right below it the A blues scale so that we can compare them.
Let's look at this another way and break down the notes and interval formulas for these scales:
We can see that the Blues Scale is the derived by taking the minor pentatonic scale and adding a "b5" (flat 5), or in the case of the A blues scale a Eb note. Thinking about the blues scale like this really makes it easy to memorize both the minor and blues scales across the whole neck.
Memorizing and learning how to improvise with each pattern is the best way to have it become part of your regular playing. Instead of memorizing all 5 shapes and then learning how to improvise with them, it is far better to learn one shape, improvise with it, then move on to the next one. Trying to memorize all 5 shapes at once is a typical mistake I see with students and it rarely works, and the student forgets the shapes because they are not using them in a practical way.
You can use the blues scale across minor and major/minor blues. You can also use it across almost any style of music. For this, its best to think of the blues scale as a minor pentatonic scale with an additional note. This way you know that it can be used across any song that is rooted in a minor key. This could be metal, country, jazz, blues, rock, funk, really anything.
Use the star system to help motive and track your progress through songs and exercises. Here is the breakdown for this exercise:
Learn and memorize each pattern, then improvise with it on top of a blues or backing track in the key of A.