In this bite-sized lesson, Joe Satriani provides some useful exercises for improving your legato technique.
From Satch: "Here’s a great exercise that’s cool because it’s a repeated symmetrical pattern that has nothing to do with any specific key signature [FIGURE 17].
"I play three notes per string, picking each string only once and then sounding the next two notes with hammer-ons. Then you can change the fingering to this [FIGURE 18] or this chromatic pattern [FIGURE 18, the last pattern].
You will find that every note that you play on every fret will require a slightly different attack with the fretting fingertip."