Measure all ingredients accuratley.
Arrange the oven racks so the muffins will bake in the center of the oven.
Preheat the oven for 10-15 minutes.
Fill muffin cups two-thirds to three-fourths full. If the batter does not fill all of the cups in your pan, fill the empty ones with water. The muffins will bake more evenly.
Muffins should go into the oven as soon as the batter is mixed, unless the instructions tell you otherwise.
Check for doneness 5-7 minutes before the end of the recommended baking time to avoid overbaking. Muffins are done when a toothpick inserted near the center comes out clean. If the muffin has a filling, make sure you insert the toothpick into the muffin, not the filling.
Cool the muffins in the pan for 5 minutes, unless the recipe directs otherwise. They're best served warm right from the oven.
If muffins have tunnels or peaks... It could be the batter was overmixed.
If muffins have a bitter taste... Too much leavening was used.