Watch the The Diminished Scale online guitar lesson by Robben Ford from Solo Revolution: Diminished Lines
The diminished scale is made up of a series of half steps and whole steps. So, just so you understand, the first move you make is a half step. So, here we establish it here in the key of A and we play a series of half steps and whole steps. It's kind of cool how it falls on the guitar, because you're playing one finger after another, using all four fingers. It's a great exercise, especially for people who are slow to use their ring finger or pinky finger. Make sure to practice it going up and down, and in every key!