This is a basic start up to playing a solo over a typical 1-4-5 blues progression.A lot of rockers just rip through the 3 chords using the same scale!This not not blues playing.If you listen to a good blues guitarist,you will be able to hear his licks change with each chord.He is playing a lick that is fitting to the chord being played!He is not just ripping away haphazardly!There is some thought and intelligence going on within his solo.This style of playing is close to jazz,just on a more related and basic way.The jazzers use the same concept,but take it to a more advanced and intricate level.We are talking chord/scale relationships here.This is just to get you started,and that can really be the hardest part.Not having a clue of where or how to start makes the initial move ever so complex,but it's not.
Let's take a 1-4-5 progression in the key of A,a popular guitar key.And remember this can be transposed to any key!Once you get a grip on this start to apply the same idea to other keys,and ones you are familiar with,will make it easier,like E or G or D.
OK,a 1-4-5 in the key of A is ...
//A /D /E // or A7 to D7 then to E7.And along with that you could color the chords D and E by playing them as D7add9 and E7add9.The ol' James Brown chords :-).So you have Adom,7 to D9 to E9 .To make the scale to play on the 1 chord/A7,let's play an A minor pentatonic,and you can play A minor pentatonic Blues scale by adding the D# or Eb note to the A minor Pentatonic scale.
Now,what to play on the D9 chord.Let's play an A Dorian mode or,same thing a D Mixolydian.This fits nicely with the notes in the chord.
And lastly the E9 chord.Let's keep this bluesy sounding :-).So let's play an E minor Pentatonic or an E minor Pentatonic Blues scale.
Take each chord and it's scale and play slowly starting off.
So the formula is...
A7 Chord > A minor Pentatonic or A minor Pentatonic Blues scale.
D9 Chord > A Dorian mode or D Mixolydian mode.
E9 Chord > E minor Pentatonic or E Minor Pentatonic Blues scale.
Remember...go slow and practice just one change at a time then 2 changes,then,all 3 chord changes.You will begin to hear the solo beginning to change with each chord change.This is so much cooler than just ripping all the time,with the same scale!