Basecamp published their guide to internal communication recently, and it is insightful and excellent.
Meetings are the last resort, not the first option.
If your words can be perceived in different ways, they'll be understood in the way which does the most harm.
"Now" is often the wrong time to say what just popped into your head. It's better to let it filter it through the sieve of time. What's left is the part worth saying.
Write at the right time. Sharing something at 5pm may keep someone at work longer. You may have some spare time on a Sunday afternoon to write something, but putting it out there on Sunday may pull people back into work on the weekends. Early Monday morning communication may be buried by other things. There may not be a perfect time, but there's certainly a wrong time. Keep that in mind when you hit send.
I highly recommend that you give the article a read.