Step 1: How much does it weigh?
A cup of all-purpose flour, properly measured, should weigh 120 grams. The flour measured incorrectly by dipping the measuring cup into the flour can weigh anywhere from 150-160 grams. Try it out!
That's like 30% more flour than the recipe needs!
A cookie or cake made with flour measured this way will be tough and dry. Sauces will be too thick, and pie crusts crumbly and dry.