Curious to know the current strategies of peers in their working environments. Here are/were mine:
Now: Communication primarily takes place in person and on email. We use Keynote docs (stored in a shared location) for presenting design options, and put annotated screenshots on a github wiki for spec. No more work is done than needed, meaning, if a decision can be communicated in person once (e.g., "it should be 60% opaque"), it's not later recorded. This comes at the cost of having a 3rd party/QA unable to verify, but at the benefit of expedience. Frequent f2f meetings.
Good: lightweight, easy to iterate
Bad: storing in a document feels outdated, no documentation of f2f decisions