Popcorn is one of the best snacks around. Cheap, healthy, easy to make, and pretty diabetic-friendly. Although popcorn is pretty high on the GI scale, a cup only has 5g of carbohydrate, so it's not hard to fit into a managed carb diet. And it counts as a whole grain.
The popcorn in microwaveable bags might be convenient, but you don't need all those added chemicals just for convenience. Making popcorn "from scratch" isn't any harder.
Popcorn and a paper bag are all you'll need. One pound bags of popcorn can be found on the same shelves as microwaveable popcorn for about $1 a pound. This is one of those cases where the cheaper option is better for you.
Pour your popcorn kernels into the bottom of the bag until they just cover the bottom.
Fold the top of the bag down. Alton Brown says you can staple the bag shut and the small amount of metal won't cause any microwave explosions. But really, that's not necessary. It's a waste of a staple; I've never had a bag unfold itself all the way in the microwave.
Place the bag in the microwave and set the microwave for 3 minutes. (There's no photo of this step, but you can imagine a microwave, right?) Stay within hearing distance of the microwave as the popcorn pops. When the popping slows down, stop the timer. For me this is usually around 2 minutes 30 seconds, but microwaves vary. The longer you leave the microwave running, the fewer unpopped kernels will remain. But you also risk giving the popcorn a faint burnt taste if you leave it in too long.
The bag expands a bit, but see, no popcorn explosions!
The angle is distorting this a little, but the bag is about 2/3 full now.
Pour the popcorn in a bowl. Choose a bowl that has more than enough room to hold all your popcorn, because now we're going to add our flavorings.
My favorite combo is Earth Balance (trans-fat free margarine), soy sauce, salt, and nutritional yeast. I mix the melted EB and soy sauce together beforehand so I don't end up with too strong of a soy sauce taste in any one handful of popcorn. Drizzle some liquid flavorings, sprinkle some dry flavorings, and repeat until you're through.