Return the pan to the heat. The popcorn should begin popping soon, and all at once. Once the popping starts in earnest, gently shake the pan by moving it back and forth over the burner. Try to keep the lid slightly ajar to let the steam from the popcorn release (the popcorn will be drier and crisper). Once the popping slows to several seconds between pops, remove the pan from the heat, remove the lid, and dump the popcorn immediately into a wide bowl. With this technique, nearly all of the kernels pop, and nothing burns.