In our interface design work here at HubSpot we talk a lot about the unwritten rules that we design by. They come up in design reviews, in hallway conversations, and in heated chat rooms. I'm sure we have many dozen of both spoken and unspoken rules overall.
Some of these rules are hard-and-fast ones like "One primary action per screen," which means that we try for each screen to have a single primary purpose that customers use it for. Others are less formal sayings like "Great design is invisible," by which we mean that if your design is working it's not necessarily apparent to the people using it.
I'm sure I could have written twenty more design principles, but these seemed like the big ones. They implicitly guide a lot of our design efforts here at HubSpot, from designing dashboards to setup flows to list pages. (although each designer has their own principles as well). Most importantly, these principles help guide us back to simplicity when we've over-complexified a screen.
So let us know you think...would these principles help you when you're in the midst of design?