Pop popcorn using a hot air popper or other any popcorn machine you have. Place popped popcorn in a large bowl, removing any kernals. Set bowl aside.
You can use microwave popcorn if you want. You'll need about 2 1/2 to 3 bags, depending on how well it pops up. When I do use microwave popcorn I usually use the light, so there's not a lot of salt and butter on it. I have used the movie theater butter kind before and it's delicious with the caramel sauce poured over it, it's just a little richer tasting with the buttered popcorn.
I use the cold water test to check for the softball stage. I take it off the stove as soon as it forms a really soft ball, I don't let it get to a firm softball because I like my popcorn to stay soft and gooey. Once it comes to a full boil, it only takes 4 to 5 minutes to get it to the right softball stage.