I usually put all the same stuff in each front pannier each time, last tour had tent (excluding poles) and air mattress and flip flops in right side and all clothing excluding outerwear and rain gear in other front pannier. (It was a one and a half month tour, so I had a couple changes of street clothing for sightseeing too, thus the large volume needed for clothing.) I often strap rain gear to the top of a front pannier where it is very accessible - the Ortlieb front roller has a strap that goes over the top and works great for this.

Rear, I always remember which of my rear panniers has the tools in the very bottom - bottom because they are heavy - I remember which side because I do not want to empty two panniers on the road to get to the tools if I only need to empty one. I do keep a small minimalist multi-tool in my pocket to minimize the need to get to the bigger heavier tools in case I need to tighten a bolt or adjust a cleat spring on a pedal or something simple that a minimalist one will do.

I put my sleeping bag and some outerwear in a compression stuff sack, that fits perfectly oriented horizontally in the top of one rear pannier.