i don't actively pull up. i just pedal, and maybe exaggerate the stroke a little - pulling back through the bottom and forward over the top - while climbing or out of the saddle. however, if i get on my bike with sneakers or ride a bike with platform pedals, i immediately notice the difference and feel like my feet are lifting up off the pedals on the upstroke. i'm just not conscious of it while actually riding clipless.

EDIT: just wanted to add...i think if you're conscious of pulling up and feel like you're adding a lot of power that way, it might be counterproductive, because it means you're overemphasizing the upstroke relative to the downstroke. you should be able to get more power from the downstroke, and while being clipped in allows you to add a little on the upstroke and make the motion more efficient, it shouldn't be the dominant source of power. not an expert and have no real evidence...just my thoughts.