The most important thing about making a great crepe is allowing the batter to rest, allowing the starches from the flour absorb the liquid and produce a tender texture.
1 cup flour
2 teapoons sugar
300 millilitres milk
2 tablespoons brown butter (brown over medium-high heat for about 4 minues)
Add the flour and salt to a bowl. Add half the milk and the egg, whisking all the while until smooth. Add the rest of the milk and whisk until smooth. Add the browned butter.
Add the sugar or any other flavourings, such as lemon zest or vanilla. The batter may seem very liquid but that is what you want.
Allow to rest a minimum of 20 minutes (ideally a couple hours or make it the night before).
The batter may thicken while resting. It should be the texture of light cream. Thin it with a teaspoon of water if necessary. (Remember, your first crepe is your test crepe, you can always thin it more.)
Heat a pan over medium. Rub it with a bit of oil or butter. Add about a ¼ cup batter off the heat and rotate the pan until the batter spreads thin. Use just enough batter to coat the pan.
Put the pan back on the stove and cook for about 1 minute. Check for browning. When the top of the crepe starts to look dry, flip it.
It will need less time on second side. When done, slide it out of the pan on to a warm plate. You can make crepes in advance and reheat when needed.