Pour 2 cups flour into a mixing bowl. Add sugar and salt and stir. Add 1 cup shortening. With pastry cutter, cut in the shortening until the mixture resembles sand.
Add 1/4 cup of milk at first. Sometimes you will use the full 1/2 cup of milk and sometimes not depending on time of year and humidity, etc. With a large fork (I like to use a large serving fork for example) stir until it "comes together" and STOP! Over mixing is what causes a tough dough. With floured hands, form a dough ball then flatten a bit into a "disc". Wrap in plastic wrap and set in fridge for about 20-30 minutes to rest and allow the dough to relax, making it easier to roll.
During the last 10 minutes of resting, pre-heat oven to 350 degrees. When ready, on a well floured surface (you can use less flour if you have one of those pastry discs with a pastry cover on it) roll dough out to whatever shape you need it for the pan or pie plate you are using. "Dock" the crust (poke holes in it with a fork, toothpick or other utensil to make small steam release holes) before baking, usually bakes for about 25 minutes if you are using for a no-bake pie filling to add in afterwards. For crusts that bake with the filling, follow your recipe's instructions.
This recipe makes enough dough for a double crust pie but I love crust so much that I sometimes use 3/4 of the dough for a thicker crust then roll out the remaining dough, cut into strips and sprinkle with cinnamon & sugar and bake, making YUMMY treats!
Why not butter? Butter gives good flavor but makes crust hard/crunchy not light & flaky. Shortening really is the key. I've known people to combine both like: 3/4 shortening to 1/4 butter but I stick with mom's success! I suppose butter flavor shortening would work.