In reply to Lefties and lettering:
On some occasions I have used the method seen in the top line in the middle of the illustration above. So going from left to write on a regular piece of paper and inverting only the stroke directions. It's probably the most easy way to start with, when one just takes a short calligraphy workshop.
It has it's limits though. It only works for simple and more static letters. You can't do an end swash on the right side of course, because this is where you actually start …
But the methods seen on the right side remove all limitations for lefties. I saw some great examples of this technique on youtube some years ago, but unfortunately they were deleted. If I remember correctly, that guy, who created really stunning work, combined both methods. He used that special pen holder AND had the sheet turned 90 degrees. As a result, the position of the hand is actually pretty similar to regular left-handed writing.