We organize our columns in Trello around our scrum process. Our Proposed column is called the Wish Heap. It's where stories go before they're groomed (titled as user story, acceptance criteria defined, sized) and added to the Backlog column (or To Do) ready for work.

First rule I try to get everyone in the org to follow: all work done by devs has a card. A dev gets approached by a manager who just needs one quick thing done, shouldn't take more than 5 minutes: "That's great. Can you throw it on the Wish Heap or talk to the scrum master?"