When we had our house built I thought having a two story house would be great, but now not so much. Stuff from upstairs comes downstairs and sits around, stuff from downstairs goes upstairs and does the same, but not nearly as often.
I try to live by the rule, "don't go back up empty handed" meaning every time you go upstairs take something back that belongs up there. Well, that doesn't always happen and I don't want to nag about it, the issue isn't worth the frustration.
Here is what we are doing to combat the issue:
I thought about our laundry routine which involves baskets small enough for each child to carry upstairs and put their own laundry away. They then return the basket to the laundry room for the next use. Works great!
So I decided to get baskets for each child and myself (yes I am guilty, too) and put them in a place we could easily see them and collect the things that belong upstairs. A clutter landing zone. Now when the basket is full or as needed everyone takes the basket upstairs, puts things away then brings the basket back down.
By taking a routine that already works for us (laundry) I applied it to another clutter hot spot and now clean up time is a piece of cake!