Label Everything Properly.
You'll never catch my daughter storing t-shirts with long-sleeve t-shirts together! Inspired by her diligence, I always make sure that I don't mark a box or cabinet's contents as "financial records" and then throw some other notifications in because they kinda-sorta fit the label. A year from now, I know I'll be looking for those documents and have no clue where I put them. I take the time to be specific and make sure my label makes sense for what's actually stored in a file, cabinet, drawer, whatever. No labels marked "miscellaneous" allowed!