Microwave popcorn comes in those U-shaped envelopes, but the popcorn, itself, is in the bottom of the U. I've found that if I shake and manipulate the bag that I can move more of the kernels into the two sides of the U, thus exposing them more openly to the microwaves.

I've seen a distinct decrease in the number of kernels that fail to pop or only partially open. No kidding.

I've done a couple of quick comparisons, so far.

Anybody else hit on this?