Just remember 2 words and you would never face this issue ever again.
OIL & HEAT
The most common reason why food sticks to Cast Iron is Because either Pan is not Hot enough or it is too hot. As Cast Iron Retains heat well, You just do not need to keep the flame at high setting as you do for other cookware. If the Cast Iron is not hot enough you would still feel food sticking to the pans. At ideal temperatures the food will automatically detach itself from the pan.
The other reason Food sticks is that food is being cooked without enough oil. Use of oil helps prevent food from sticking and adds a natural non stick layer (seasoning) as you cook.
Cooking Tips:
Preheat your skillet for couple of minutes so the pan has hot enough. Put few drops of water and the sizzling sound would confirm the pan is hot enough to add oil. Add Brushing of oil or as per your need before you add food. Shimmering of oil indicates the pan is ready for cooking.
Putting Food in cold oil would make the food soak all the oil and if oil starts to smoke it means pan is simply too hot. Once ideal Temperature is achieved lower the temperature to medium or medium high and enjoy Non Stick Healthy Cooking.
Add enough oil to the pan before adding food. You’ll want to use enough oil to coat the bottom of the pan. Foods that are prone to sticking, like eggs, may require a bit more oil, while fatty foods, like chicken thighs, don’t need quite as much oil to keep from sticking. If you use butter, it can still be helpful to start with a thin layer of oil to prevent it from sticking to or burning on the pan.