Movie Theatre Popcorn at home

After years of having it on my wish list we finally got a movie theatre popcorn machine!!  It came with the cart and so it fits nicely in our family room.  So far we've been experimenting with the best recipes to make the popcorn-
You can purchase packages that have everything you need for a batch of popcorn, but they can be kind of expensive (about $1/batch) so we tried another route.
Buying popcorn kernels in bulk is super cheap! (like $4 for enough to do 20 batches or so I'm guessing)
I purchased sunflower oil- one large bottle for around $4.  We've made probably 10 batches and aren't even 1/4 through the bottle.
Popcorn salt you can find by the seasonings/baking items in your grocery store, it runs about 50-80 cents and will last forever! (this salt is a fine powder so it's much better on popcorn)

I figure by combining and using the ingredients this way we can make a batch of popcorn for pennies on the dollar compared to the pre-packaged batches.

Some tips I have found so far-

1. There are different types of oils you can use.  Although I've heard coconut oil is amazing I couldn't bring myself to buy it yet because it was in a crisco-like form (solid versus a liquid)  so if I try it I'll let you know.  Sunflower oil is great, and there is also a popcorn oil that supposedly has a butter flavor to it but honestly I can't taste it.
2. Make sure you heat up your kettle with enough oil to coat the bottom before putting in your seeds & salt
3. Add popcorn salt to your seeds when you put them in the kettle. (as opposed to just sprinkling salt over the finished popcorn) it will salt the kernels more evenly.

I've also heard you can make kettle corn by adding sugar! (I'm not a big kettle corn fan so we haven't tried this one yet)

Feel free to comment with any other tips you know about!