If you've ever wondered when you should be playing Major or Minor scales then this tip might help to put a bit of sparkle in your solos.

For a standard 12 bar blues progression of (I - IV - V), I recommend the following approach.

Whenever the (I) chord is playing, try to use the Major blues scale of the key you are playing in. Although you can play minor over the (I) chord, I think it sounds better to play the Major Scale. If you listen to BB King for example, you will hear a lot of the Major scale being played over the (I) chords.

For chords (IV) and (V), you should definitely stick to playing the Minor Blues or pentatonic scales. The combination of switching from Major to Minor really sounds great.

Give it a go and see what you think.