I've been making french toast since I was very little and have tweaked it over the years.
Preheat your pan to a medium low heat. While pan is warming up mix your eggs, sugar, cinnamon and milk together. Beat with fork or wisk.
Once pan is warm, coat pan in a good amount of butter. Dip bread into egg wash, coating each side and place into pan.
Flip bread when the bottom side has browned. Remove from heat when both sides have been browned. Repeat this process until all of your bread has transformed into french toast.