I have made popcorn in the microwave two ways, one using a brown paper bag and the other using a glass pyrex safe for the microwave bowl.
It is easiest to make popcorn in the microwave using a brown paper bag.
1/2 cup popcorn kernels
1 tsp oil (such as canola) or 1/2 tsp oil and a few thin slivers of butter Note: fat is OPTIONAL
1 brown paper bag
Microwave for 2 minutes
Mix the popcorn kernels with the oil. This method also works with NO fat, just the kernels in the bag, in which case I prefer to use only 1/4 cup kernels. I buy whatever kernels are on sale.
If using oil, I mix the oil with the kernels in the measuring cup. Any type of seasoning can be added at this point and mixed into the oil and kernel mixture. Place the kernel/oil mixture into a paper bag. Fold the top of the paper bag twice, about 1 inch for each fold. Place in microwave for 2 minutes. I have reused the paper bag shown below a few times.
If using "NO fat," I prefer using 1/4 cup kernels and stop my microwave at about 1:45, at which time there are almost no un-popped kernels in the bag.
Fold the bag over twice, about 1 inch for each fold.