The exercise of the left hand without regard to the right on hammer-ons and pull-offs is crucial (of course for left handed guitarists, the opposite would be true). Whether you like to incorporate right (left) hand hammer ons (or tapping), or whether you're planning a move that has you coordinating the pick in the right (left) hand, you can practice merging these into the technique separately.
Here's a couple of great exercises from some very popular tunes.
Starting slowly, I suggest you use the ring and and index fingers. If you'd like, set the Tempo at the bottom of the page, set the Loop to Forever and play along with the riff as a sort of metronome tool. Or, set the Tempo, and click on the metronome icon to the left of the tempo box. This way, you might set goals to achieve better speed.