Dynamics and articulation are a large part of expression in music. We often focus so much on getting the notes right that we forget that they are a very small part of the expression we are trying to accomplish in music. It's possible -- and effective -- to work on dynamics and articulation without regard to notes, and then apply what you learn to a familiar line or scale.

Let's say you want to work on making smooth crescendos and diminuendos and using hammer-ons and pull-offs. Break this down into separate practice routines, and then pull them together. Sticking to one note, get louder, then softer at a rate that you've chosen (e.g. get louder for four notes, then softer for four notes -- or eight, or sixteen -- your choice).

After this, practice hammer-ons going up a chromatic scale (one fret at a time) and pull-offs going down. Then combine the two: play your chromatic scale on one string, varying the dynamics as you did with your one note. Where can you go next with this to increase your expression?