This is potentially more information that you want, so feel free to take whatever you want from it and ignore the rest.

Back in my training/racing days, we used to divide the pedal stroke into four segments: push down, pull back, lift up and kick over. The push down part is something we are all familiar with. The pull back happens at the bottom of the down stroke, and the feeling you should get is the same as when you scrape mud off the bottom of your shoe. Pulling up is pretty self-explanatory. Kicking over the top is the mental picture you should have of the fourth segment. We did laps on level roads where we had to use just one of the segments at a time. Of course, it feels really weird and is nearly impossible to keep going for very long but you are working to develop the muscle memory. Then we did laps where we would spin as fast as we could, trying to incorporate all of those segments. That would smooth out the transitions and help us put it all together. In practice, pulling up is something that isn't done a whole lot although it's talked about a whole lot. Studies have been done on pro riders that demonstrate that there is still some downward force on the pedal during the "upstroke" in typical riding circumstances (like when you aren't specifically concentrating on pulling up). When your cadence is slow (hard climbing out of the saddle or starting your sprint, for example) you can indeed pull up. However, it is of use to learn the pulling up part of the pedal stroke because you can still reduce the amount that you push down and thereby improve your efficiency. The crowning glory of all of this training was when we had to do laps with one pedal removed. That's the test of whether you are using the full pedal stroke.

Interestingly, 12 years after I last rode my bicycle, this muscle memory was still near the surface and it came back pretty quickly when I started riding again this summer. I guess it pays to train. I think that the efficiency of my pedal stroke helped me keep up with my kids, who are clearly in better physical condition overall.

-soma5