Years ago I copied this recipe from an old beat up copy of Quick and Easy Fast Breads. It's one of my favorite fast muffins to make because it always turns out well, and because it's such a basic recipe you can throw anything in (fruit, nuts, seeds, chocolate chips) and it still works.
2 cup unbleached flour
2 tbsp sugar
2 tea baking powder
¼ tea salt
1 cup milk
1 beaten egg
¼ cup oil
My shorthand on the instructions reads:
"bake 425 for 25 min in well greased muffin tin.
"Let cool before flipping out."
If you're not familiar with quick bread theory, the idea is to combine your "wet" ingredients and your "dry" ingredients separately and when you put wet and dry together don't overstir. Just fold it together enough to make a blended but still lumpy batter. Then add the fruit, nuts, whatever extras you want. Still being careful not to overstir (overstirring makes a rubbery muffin).
The proverbial handful of blueberries is always a great extra to add in, and one of my favorite variations is to add about 1/2 bag fresh cranberries and roughly 1 cup citron, possibly some pecans on top if I have any to hand.
The muffin tin needs to make 12 good sized muffins, or 9 largish muffins, or 6 giant muffins. You'll need to adjust the baking time accordingly -- don't let smaller muffins burn just because I said my oven takes 25 minutes.
... and the "flipping out"? Well, I'm sure you can handle that with no further explanation. :-)