I just realized my oven rack was in the wrong spot for years...
I kept getting burnt bottoms on my cookies, no matter the recipe or pan. Last week, my friend watched me bake and said, 'Your rack is way too high, dude.' I moved it down one slot, to the middle, and my next batch came out perfect. I guess I never read the manual when I got the oven six years ago. Has anyone else had a simple fix like that for a long-running baking problem?