To get the biggest, fluffiest kernels of popped corn, use good-quality popcorn, and store and cook it correctly. Most hounds feel that Orville Redenbacher popcorn sold in a jar pops up fluffier than generic brands. Storing the jar in the refrigerator preserves the kernels' moisture, which makes for better popping. Try nestling a little open container in the jar and inserting a damp paper towel or cotton ball into it to give the kernels extra moisture, suggests greygarious; when the water evaporates, add more.
weezycom makes popcorn on the stovetop in a soup pot with a mesh splatter screen instead of the pot's lid, allowing the steam to escape, and says the popcorn is fluffier and more tender this way. visciole recently got a Whirley-Pop popcorn maker and says, "It makes far fluffier popcorn than I've ever made in a regular pot, no matter how careful I am to release condensation. If you eat a lot of popcorn it's worth the 20 bucks or so."
Discuss: How to pop really fluffy popcorn?