I make literally hundreds of crepes weekly, (both sweet and savory).
My standard recipe is as follows.
In a blender
1 cup water
1 cup milk
1/2 stick melted butter.
good pinch of salt
Blend for a minute or so until well incorporated.
While running...gradually add up to about a cup of A.P. flour.
You are looking for a consistency of thin pancake batter.
Refrigerate for about 30 minutes or so to relax the gluten in the flour.
If it is too thick....add a little milk.
Too thin add flour and blend in.
Take a non-stick pan (I use 10") and heat to medium.
If using a 10" pan, use a 2 oz. ladle to add batter.
when pan is hot, brush with butter and add batter on one side while holding pan in hand.
Swirl pan to coat entire bottom with batter.
If crepe browns immediately, pan is too hot. Let crepe cook until you see the edges begin to dry out and brown. Flip and cook on the other side for about a minute.
Remove to plate and cover with a sheet of wax paper
Keep cooking and stacking.
Crepes can be frozen or used as needed.