I think the biggest improvement in my pedaling came from simply relaxing my ankles.

This makes my heel drop below the toes at the top of the stroke and adds some springiness to the motion, making it smoother. It also ends up making the kick-back section at the bottom of the stroke easier because this way the calf muscles get added into the mix.

What did all this mean for me? I could go up the same hill faster in a higher gear with less fatigue.

The downside of all this is you might end up having to wait at the top for everyone else to catch up