Grease a frying pan with about 1 tablespoon of butter. Crack two to four eggs right into the pan, take a fork and just keep stirring them gently. Cook to taste, usually most people like them not quite dry. I like to mix in salt and pepper as they are cooking. Serve.
I like to put a generous shake of Frank's hot sauce on scrambled eggs, my wife prefers ketchup.
Some people add milk to scrambled eggs as they are cooking; I do not.
It's easy to add things like chopped onions, or bacon bits, or cheese to scrambled eggs while they are cooking but it's not necessary.