Should I turn the cards from side to side, or top to bottom?

I don't know about you, but this is a question that always made me wonder: especially if I came up with a spread with a large percentage of reversed cards. The following is from Tarot Classics, by Stuart R. Kaplan:

According to Kaplan: "The diviner should turn the cards over from left to right, thereby assuring that the cards continue to point in the same direction as placed on the table by the questioner."