King Arthur Flour has a recipe for basic muffins that I'm experimenting with (I really like my recipe for banana and pumpkin muffins, but was looking for a basic recipe where I could use things like berries, apples, peaches, etc.). The above picture is a batch I made with chopped apples and cinnamon.
There's a tip in the KAF recipe for getting high crowns (vs. flat tops) on your muffins like you see in bakeries. You start with your oven at 500°F and then drop the temperature to 400°F as soon as you put the muffin batter in the oven. It works!