To begin with you'll learn a 12 Bar Blues Shuffle in the key of A. So first of all, lets recap the notes of the A Major scale. Take a look at the scale degrees. 

What notes are at 1, 4 and 5?

A, D and E

Now, when we refer to chords we use Roman Numerals so 1, 4 and 5 is of course I IV V. And that's it - our I IV V chord progression! 

So in the key of A our I IV V 12 bar blues chords are A, D and E.

Now we know which chords make up the I IV V progression we need to have some kind of order in which to play them. And this 'order' is known as "The Form"

The most basic 12 bar blues 'form' is as follows: - 

4 Bars of the I chord (A in this case)

2 Bars of the IV chord (D)

2 Bars of the I chord (A)

1 Bar of the V chord (E)

1 Bar of the IV chord (D)

1 Bar of the V chord (E)

1 Bar of the I chord (A)

...and back to the Top! (i.e. repeat this progression). To practice this 12 bar blues start out in the key of A using open 5 chords (power chords) playing a simple shuffle rhythm to get that all important swing feel and the 12 bar blues form engrained into you.

Jamming with the Wolf... 

Use your knowledge of the 12 bar blues form, in the key of A  to jam with Howlin' Wolf with these great 12 bar blues standards - Built for comfort and Killing Floor.