Nothing can clear the clutter from your head as much as getting away from it all—if just for five minutes. Take a walk around the office, in the parking lot, down the street, through the park, or across the field. Start by thinking about as little as you can (nothing is ideal). Then slowly let the topic you’ll write about enter into your consciousness. Visualize the finished form of the document you have yet to compose. Read what it says. Make sure you have a pad and pen in your pocket to jot any ideas you want to remember. Now you’re ready to start drafting that message. Get back to your desk—hurry!
Here are links to books on writing by Philip Vassallo: