Watch the Legato Stretches online guitar lesson by Jennifer Batten from Rock Sauce For Lead Guitar
Hammer ons and pull offs sound a lot more fluid than picking every note. It's also easier to play faster when you're not picking every note. Even though I normally finger my diatonic scales with two or three notes per string, I'll re-finger to have three notes per string if I'll be doing a flurry of hammer ons and pull offs where I only pick once per string. I'll show you another texture of playing unison notes by stretching the left hand to hit the same note on two different strings.