First lets make basic popcorn. Heat oil in a pot enough to hold the popcorn.
Once hot, add the corn kernels and give it a stir. No need to keep stirring but just one time.
When it starts to pop, cover with a lid, with slightly opened for the steam to escape.
At one point of time, the popping will reduce. Give it a shake. If you don't see popping for a continuous 30 sec. Switch off the flame.
Now lets move on to make caramel popcorn.
Heat sugar in a heavy bottomed pan. Let it melt in medium heat. There will be golden hue as it melts.
Do not over mix as there is chance of crystallization. At the same time, don't let it burn (deep dark in colour). So keep the flame low or medium.
Once all the crystals melt and you have a liquid golden coloured syrup, add butter and salt. Mix well.
Switch off the flame and immediately add popcorn to it. Mix well to coat well in the heat itself.
Spread over a tray and let it cool for 5 mins.