Put the popcorn, oil and sugar into a large pot. Partially cover and cook over medium-high to high heat, sliding the pot back and forth constantly over the burner, until the popping stops. Remove the popcorn from the heat immediately and sprinkle it with salt, if desired.
Let it cool and then place it into a big bowl for munching, or put it in individual bags for private munching :)
Notes
To make Cinnamon Kettle Corn, add 1 teaspoon of cinnamon to the oil, along with the sugar.