About the trash
About the trash, I've lived with a few people and moved around a lot, had a lot of neighbors. I would go to the neighbor and say: "hi, I just wanted to say that it would be nice if you cleaned that up today." then do some smiling and wait for a reply or just say "thanks in advance".
You could also clean it up for em, only because it's the first time, (obviously act different if it happens again) I would even buy em stuff to clean with. :-) Being treated like a little kid works on all people, hahaha Makes em furious and speechless.
I just manage to make em say: "Oh, you cleaned everything up....wow.....tnx. no, no, it wont happen again." Do be careful they will try to make it sound like you've accomplished a miracle, "an impossible task".
I bet it's one of those cases of thinking something is a fact as it's really decision and thinking it's decision as it's really pure fact. Your neighbors/people you live with, behave in just the way you make em behave, pretty much like anyone else ^_^