Maintaining a cast iron skillet (Cleaning and seasoning)

I just bought my first cast iron skillet to use to grill meats on a table
top grill. I have a few questions about how to properly season and clean it.

I have read that you should never use soap or detergent to clean cast iron. I have also read that you should never use soap or detergent to clean cast iron. I have also read that you should never use soap or detergent