Hi Frankie, guess who?
First off, anyone who's not used diminished chords 'cause they feel their "complex" or just "decoration", should actually try a little experiment. This is simple, so give it a shot.
Play a simple 12 bar blues. Just E, A and B7.
Remember each set of 4 strokes (beats) represents a bar.
Play the A7 chord with the middle finger on the 4th string 2nd fret, and the ring finger on the 2nd string 2nd fret.
OK, here goes the diminished adventure.
When you get to the last 2 beats of the 2nd bar, put your index finger on the 5th string, 1st fret.
Replace the A7 in the 6th bar with the chord you just played in the 2nd half of the 2nd bar.
Play that same chord for the last two beats of the 11th chord.
Simple, and should sound very good (and a little jazzy). You've just used an A# diminished to make your blues a little fancier....and that's just the beginning.
I'm getting writer's cramp (and battling a migraine). If someone can do a simple explanation of the Diminished and show a couple of positions, we should be on our way.