I take more screen shots than the average Joe. A picture in my mind is worth a thousand words. I have seen it so many time in technology shops that a simple screen shot will save so many back and forth email exchanges, and possibly meetings.
With mobile phones, it is so easy to do so and once you get the hang of it, you'll find yourself sending screenshots all the time.
On a Mac , I always forget the keying sequence to do so. So here its is.