I've cooked scrambled eggs everyday for the past week. We could go back and forth about the best ingredients to add to eggs. But that would be pointless because all people like different things. here a few undeniable truths to make sure you have the best scrambled eggs:
Temper Your Eggs - They will cook more evenly if they are brought to room temperature first. Let them sit out to warm up or if you are in a hurry run them under hot water for 20 seconds.
Well Oiled Pan - This is probably the most obvious. If the eggs are sticking then its not gonna be pretty. I use a 10" cast iron pan for everything and I've found that Avocado Oil works better than plain old canola oil.
You must whisk it - Whisk those eggs. How much you whisk and the ratio of whites:yolks are the two biggest factors in the fluffiness.
Low Heat - Rookie move. I've made this for years before I finally got it through my thick skull to turn the heat down. Scorched eggs look terrible. If there is any brown they are still edible but your skills need more honing.
That's it. Scramble away and enjoy.