'Go to the range with a buddy. Have the buddy load your rifle but have them either put a round into it or not put one into it. When you pull the trigger you will know immediately, no one needs to tell you, it will be obvious. A lot of people are very surprised that although they knew the gun may not be loaded, they still flinch. Flinching is involuntary and can be detrimental even if it is just your eye blinking, but most at least do a hard squint."

Tundragriz

That's the exact same technique my dad used to help see if we were flinching, and it absolutely works. This also is the reason why those who practice dry- firing as a way to improve their skills with trigger pull, don't realize they're giving up an important edge. And that is to believe, think and handle the weapon as if it's always loaded. Everything else is just good commonsense.