I saw this article on a website and I find it quite useful for people who wants to make soft and moist muffins.
Article is by Shiloah Baker
There is nothing like a tender, soft, moist muffin straight from the oven. The perfect muffin’s outside is never hard, and when pulled from its muffin paper or popped out straight from the muffin pan it comes out completely and easily. How in the world is this done?
There are some tricks to muffins that many recipes (or box instructions even) do not include.
The first trick is to NEVER use a hand mixer. Think of muffin batter as a tiny soft baby that can easily crush.
The best utensil for mixing muffins is a wooden spoon.
Make a well into the dry ingredients of the muffins and add the wet ingredients into
the “hole”. Gently fold the dry ingredients over and stir softly. NEVER stir the batter more than 20 times; count each turn of the spoon around the bowl as one, two, and so on.
It is okay to have some lumps in the batter. The object is not to rid the batter of the lumps, but to not over mix.
When putting the batter into the muffin tins, I like two methods. The first, method is to use a ¼ cup measuring cup. My other favorite method is to use an ice cream scoop with the sliding piece inside to easily push the batter out of the spoon and into the cup.