This article, From Google Ventures: 5 Rules For Writing Great Interface Copy, by John Zeratsky on the Fast Company Design site was written specifically for user interface copy, but I think it can apply to most content that we write as technical communicators. It certainly is written from the web interface perspective, but I think many of its guidelines apply across the board.
It’s first rule is “Clarity is King.” This builds off of the ubiquitous “Content is King” idea making the rounds, but here Zeratsky speaks to the issue of length. It matters not whether you keep it short or let it run long, it just matters that you communicate clearly. The guidelines within this rule about specificity, jargon, front-loading keywords, and laziness definitely help support this first rule, but the 4 other rules certainly follow in its primacy. Here’s my summary of his other rules: Skip the personality, get to the point, people will read clearly written content, and don’t wait to write the content (write it in the design phase).