With a wire whisk, mix the milk, sugar and flour until very smooth. Then beat in the eggs and add the cooled butter and vanilla.
Heat a non-stick surface until water jumps and sizzles when you flick a few drops on it. Take a small ladel and ladel some of the batter, using the ladel to smooth it into a nice circle. Cook less than a minute until the the top is no longer liquid. Then flip and cook no more than 15 seconds on the bottom. The crepes should brown just a little and should not get crispy at all. If they get too brown or crispy then the heat is too high. If they don't brown at all the heat is too low.
Usually the crepes will be set aside and reheated.
I do my crepes two at a time on my electric griddle, which is just about the most awesome kitchen utensil I have.