First, put some popcorn kernels into a brown paper bag. You can find popcorn kernels at most grocery stores (usually near the microwavable buttered popcorn) or you can go to a specialty store, like Sprouts, to get the exact amount you need.
The most you'll want to put in your paper bag is about 1/2 cup. This will yield approximately 8 cups of popped popcorn.
Fold over the top of the paper bag like you're sending your kid off to lunch (don't seal with staples or tape) and stick it in the microwave.
Every microwave will vary but 3 minutes usually does it for me. Just make sure to stop the microwave when the popping sounds stop so it won't burn.
Take the bag out of the microwave and carefully remove any remaining kernels before serving.
Add melted butter and salt for standard movie theater popcorn or use in your favorite popcorn recipe. Yum!