Place a large, heavy-bottomed pot over medium heat and add the vegetable oil.
Once the oil is shimmering, sprinkle in three popcorn kernels and cover. When they pop, you know the oil is hot enough.
Remove the three kernels, then pour in the sugar and remaining popcorn kernels; stir quickly to coat.
Cover the pot and gently shake it back and forth over the burner to prevent burning.
Once the popping slows to 2–3 seconds between pops, remove from heat and immediately transfer the popcorn to a large bowl.
Sprinkle with salt, toss lightly, and serve while warm and crisp.