Avoid cast iron. Eggs scrambled in a cast iron skillet can turn a greenish shade. This is harmless but the unappealing color change is the result of a chemical reaction between iron in the pan and sulfur in egg whites.
Don’t overcook. The heat retained in the pan will continue to cook and firm up the eggs after pan is removed from heat.
How long to beat? It’s a matter of preference. Light beating produces more dense scrambled eggs. Vigorous beating aerates the eggs, resulting in lighter fluffier curds.