Answer: JUST A COUPLE OF OIL DROPS
Step-by-step explanation:
If we´re assuming that you´re talking about homemade popcorn, the trick is simple: 2- 5 drops of oil (depending on how much corn you want to pop).
Another secret that I´ve acquired wiht several failures, is that you count 15 seconds after the last popping and if you don´t hear another popping, then your popcorn are ready! (I know, it sounds redundant).