Credit: Arthur Mount

Why it’s bad: Overmixing flour activates the gluten, a protein that can give baked goods a firm and elastic structure—delicious in a chewy pizza crust but less so in a delicate pastry.

Do this instead: Go slow and gentle for tender cakes and flaky piecrusts. When adding dry ingredients to cookie and cake batters, use the lowest speed on an electric mixer or mix by hand until just combined. A few lumps in the batter are fine. For piecrust, whether you use a food processor or mix by hand, work the dough as little as possible. Visible bits of butter and streaks of flour are desirable.