This is how I make popcorn:
Pardon the mess; I never cook alone. To make tasty, butterless popcorn, all you need is an air popper (got mine new at a garage sale for $3), seeds, a spray bottle of water, and your seasonings. I use salt & pepper, but you could use almost any spice you like.
The biggest problem with no-butter popcorn is getting any seasonings to stick. That's where the water bottle comes in. After your popcorn is popped, just spritz it lightly (not enough to make it noticeably wet or soggy!) with water and sprinkle with seasoning. Stir it up and do it once more. That's it!
My kids never ask for butter anymore! Quick, easy, low-cal, and high fiber! Try it sometime and tell me what you think.