Now that so many people are doing their holiday baking, the above linked article will help you not make the same mistakes that many people do.
I rarely bake, but I can’t be bothered with the scale, especially since most recipes are written with cups, etc, and not the weight.
I also never sift my flour or powdered sugar.
My biggest baking and cooking crime is being forgetful. I forget to set the timer or I turn the timer off and “I’ll get to it in just a second.” then I will totally forget what I was doing.
This list is great. It goes through everything that could possibly go wrong. Take a look at it and see what you might be missing before you start your holiday baking.