I truly believe searing is a work of art and when you have a work of art, you treasure that with the utmost caution.
To sear properly you need to heat up your cast iron pan with a little oil. Please note that too much oil can ruin the flavor of what you are preparing. I prefer to use coconut oil because it is healthier than other oils. The healthier products you use can add more life span to yourself. You should wait until your pan is nice and hot before you actually place your meat in the pan. You want to only let it sit until it is golden (for chicken); as for beef it needs to be a dark brown (see below for pictures).
Next, you flip it over and barely let it sit for approximately a minute and a half. You then pull it out of the pan and prepare it to place in the oven.
By doing this you will see and taste the difference in your food! Enjoy!