Why this matters
A baked good sets after gases expand, proteins firm, starches gelatinize, and moisture moves through the batter or dough. Ingredient ratios and pan depth influence all of those events. That is why a casual extra scoop of flour or a much smaller pan can change more than flavor. Measure carefully, then use color, aroma, structure, and temperature as doneness clues.
How to do it
When a recipe gives only cups, fluff flour, spoon it lightly into the dry measure, and sweep the top level. Pack brown sugar only when the recipe says 'packed.'
What to look, hear, or feel for
Flour should sit level without a compressed mound or hollow. A cup scooped straight through the bag can contain much more flour and make baking dry.
When something goes wrong
If dough is unexpectedly stiff, check the measuring method before adding liquid. Make small corrections; baking formulas are less forgiving than soups.
Try it in a real meal
Practice on pancakes, muffins, quick breads, cookies, or one simple yeast dough before making several substitutions.