When Muffins Fail to Rise
Here are a few tips that may be helpful in making perfect muffins and quick breads: Be careful not to overmix the ingredients. Add the liquid ingredients to the dry and stir only until moistened—don’t worry about small lumps.
Either use paper muffin cup liners or grease muffin tins on the bottoms and only halfway up the sides of each cup. (The ungreased portion of the cup will allow the batter to climb up the sides for a higher muffin.) Fill the muffin cups about two-thirds full unless otherwise directed in the recipe.