Ask HN: How do you manage requirements?

How do you 1) ensure people are working on the "right" things (e.g. prioritize), 2) give external entities (whether that is the CEO or the board or your grandma) visibility into the status of the project, 3) encourage communication between team members, and 4) provide a way for everybody to provide input? I've worked with many software project management tools (from Rational ReqPro to Scrum Ninja) over the years. I've also worked at large and (very) small companies. I want to put something in place that minimizes administration but provides the benefits mentioned above. What tools and process (yes, even a two-person company can have "process", but I would hope you don't have Process :) work for you?