You've Been Measuring Flour Wrong This Whole Time
If you're a fan of celebrity chef Alton Brown, you already know how he feels about measuring flour. In the words of the Good Eats host: "I have a rule in the kitchen: If you can weigh it ... weigh it. This is especially true of compressible powders like flour" (via AltonBrown.com). And yes, of course, if you have a recipe so precise it provides measurements in ounces instead of cups and you also have your own kitchen scale, well, you're way ahead of the game when it comes to measuring flour and you're already displaying some high-level baking skills.
If, however, you're strictly team scoop-from-the-bag, and you know you're not going to bother buying, much less using, a kitchen scale any time soon, that's okay. There's still a way you can measure your flour more precisely and increase the chances of your recipe turning out the way it was meant to: The baking pros at kitchen maven Martha Stewart's website recommend a method they call scoop and sweep.
How to measure flour the right way
One of the biggest baking fails occurs when you add more flour to the recipe than is actually called for, which can render your final product too dense, dry, or crumbly. Simply dipping the cup measure into the flour tends to pack it down, thus increasing the volume. Instead, what you should be doing is first "fluffing up" the flour by stirring it around a bit, then using a spoon to scoop the flour until it is piled slightly over the top of the measuring cup. Level off the flour by gently sweeping off the excess with the flat side of a knife, returning it to the flour bag or canister so it doesn't go to waste.
The difference this flour-measuring technique can make
Flour measured via the scoop and sweep method will almost inevitably be closer to the amount intended for use in a professionally-developed recipe, as opposed to one from a church or community cookbook or a family recipe, in which case your results would depend on how the recipe author did their measuring. But if you do happen to have a kitchen scale, and you want to see for yourself what a difference this technique can make in your measurements, Martha Stewart assistant editor Lindsey Strand recommends comparing the weights of a cup of flour scooped straight from the bag and one that's been spoon-filled and knife-leveled. As Ms. Strand puts it, "It's crazy to see how much of a difference it can make!" Crazy, yes, but scoop-and-sweep is a simple cooking hack you'd be crazy smart to start doing right away.