When do we need to communicate?

1.  When something significant changes

This seems obvious.  When things change, we need to tell other people
about it.  Of course, it may seem as if the change is too small or
otherwise not really worth bothering people with, but stop and think
about what the change "looks like" from their point of view.  A
"small" change from here may be a large, important change from over
there.  And sometimes, what we think is a HUGE change looks like
nothing from over there.  So we need to alert people that something
changed, when it is significant TO THEM.

2.  When we expect something significant to change

Everyone hates being "blindsided" by change.  The best way I know to
avoid doing this to people is to warn them early and often.  One of
the payoffs in doing this is that when you are providing those early
warnings, you can learn just how important they think the change will
be.  You can work on educating them if they don't see how important
the change is, or avoid overloading them if the change really isn't
significant to them.

3.  When change doesn't happen

This is hard to remember, but when change doesn't happen (either
because there was a problem or there just isn't anything supposed
to show up right now) it is probably a good idea to tell people about
it.  I.e., every now and then, just stroke the human contacts and let
them know that we are idling right now.  How often is "now and then"?
It depends on how often people expect something to happen.  If you've
been telling them things daily, and then go silent, after a day or so
they are worrying about what happened.  On the other hand, if you
normally only report once a month, you only need to say "nothing to
report" after a month or two.  Don't let the silence stretch past
about twice as long as normal reporting.

4.  When we have a question