How structured/organized are you when testing Facebook ads?

Basically, when you are testing different campaign structures, interests, ad creatives, etc., how organized are you? Do you have a notebook full of your experiments and results?

I ask this because as of right now, I am mentally remembering all the findings from my testing.

Let's say I test 10 different interests, target different locations, make changes to my ad creative, etc. I am simply mentally taking note of which performs best.

Is there some sort of SYSTEM you use? I feel like I should be way more systematic with the way I test facebook ads...