Mixing the batter too much is a common reason for dry, hard muffins. As you mix the batter, the glutens in the flour release and start to tighten. Too much mixing makes glutens proactive, creating a hard, dry muffin. Counteract this by mixing the ingredients only until the dry ingredients are moistened, even if lumps remain. Never mix muffin batter with an electric mixer. Instead, use a wooden or plastic spoon and soft, even strokes; about 10 to 15 should suffice.

Muffins can quickly burn and dry out in the oven. Baking them too long or at a higher temperature than the recipe calls for creates a tough, crumbly texture. Using a dark, non-stick muffin pan can also lead to overbaking, because these absorb heat faster than other cookware. Instead, use a shiny, well-greased or well-lined muffin pan. Bake them at the temperature listed on your recipe, and check on your muffins throughout the baking process. Insert a toothpick into the center of the muffin about five minutes before the recipe says to remove them. If it comes out clean with a few crumbs attached, they’re ready to remove. You can also tell by pressing lightly on the top of your muffin with your index and middle finger. If the impression springs back slowly, your muffins are ready to remove. If the impression stays, they need to bake longer.

Ensure the accuracy of the ratio of wet to dry ingredients. Improper measuring, especially of dry ingredients, can create a hard texture in the end. Measure flour appropriately and level off each measured scoop using a spatula or the flat edge of a butter knife. Use the appropriate liquid measuring cups for the liquids -- cups that are plastic or glass with pouring lips and handles -- and the appropriate measuring cups for dry ingredients.

Recipes are based on sea-level atmospheric conditions. At higher altitudes -- typically above 3,500 feet -- air bubbles expand and rise faster than at lower altitudes, which means moisture leaves your muffins faster while baking. Fix this by altering the amount of flour to liquid. Add 1 to 2 tablespoons of additional liquid -- using the liquid already called for in the recipe, such as milk -- for every 1 cup required at altitudes of 3,500 feet or more. Add additional moisture by using brown sugar -- cup for cup -- in place of granulated sugar.

Even a perfectly baked, moist muffin can turn stale, dry and hard if you store it inappropriately. Once cooled, store baked muffins at room temperature for up to two days in a plastic storage bag or airtight container, or covered with plastic wrap. Wrap excess muffins tightly with plastic wrap or aluminum foil or place them in a heavy-duty freezer bag, then store them in the freezer for six to 12 months at 0 degrees Fahrenheit or below.