Checklists.

Looking at what I am actually using and mailing stuff home (as well as updating the checklist).

I know I do better when I have a defined checklist than when I leave my bike sitting for a few days while I contemplate adding more stuff to the load. I also know that I sometimes bring stuff I don't use. If I don't use a spare inner tube, I'll probably still bring one next time. However, I do try to adjust the checklist based on what I use. I've also stopped a week or two into a long trip and then mailed stuff home.