I've never written any camping equipment plan down (yet), but I would probably benefit from doing so...

What I do is that I make a mental checklist in my head: What do I need for sleeping? (Ground sheet, sleeping bag, tent, whatever...) Cooking? (Stove, pots, ...) Clothing? and so on and so forth. So far I've never forgotten anything important, but I could probably cut down a bit on the weight and bulk if I had the discipline to make a list.

As I said, I am most afraid of forgetting to bring my shoes and jacket. They are not part of my pack, and if the weather is nice on departure I won't be wearing them when I pack and drive the car. It is my perpetual remember-in-the-last-minute item.