In one bowl add all the dry ingredients and combine well. In another bowl is all the beaten liquid ingredients. Add the liquid ingredients to the dry ingredients and with a few swift strokes beat them together. The mixing is held to an absolute minimum which will leave some lumps just ignore them. If the batter is mixed to long, the gluten in the flour will develop and toughen the final product.
The creamed method usually is for a richer and more cake like muffin. Cream the soft butter, sugar and then beating in the eggs one at a time. Beat with a mixer until light and fluffy. After creaming the butter, sugar and eggs, the dry ingredients are added alternately with the liquid ingredients starting with the dry and ending with the dry ingredients.
I have always been taught to scoop the muffins out and put them into the oven after mixing. After reading an a blog, and I can't remember who's but they work in a bakery. They mix their muffins and put them into the refrigerator and don't bake them until the next morning when the shop opens. They probably started do this just to make the morning rush easier to handle. They discovered the muffins came out taller and more perfectly shaped. I tried it and it does make a slightly taller and better shaped muffin. You will need to lengthen the baking time by about 2 minutes or so since the dough is cold.
So chill the dough, even 2 hours makes a difference but you can let it sit overnight which might make your morning easier to handle.