I like the version without the pleats (version A or B, if you look at the pattern on the Vogue web site) and would put the plaid on the diagonal either on the sides or on the front/back. But which to do? What do they do in RTW? I did some research to find out.
I didn't find much in the way of mixing the directions of the plaid in the style that I want to do, but I did find this one that shows the diagonal plaid on the sides (Nanette Lepore skirt in a photo from Saks Fifth Avenue website).
Diagonal ( from Ann Taylor Loft web site):
Horizontal/vertical (from Ralph Lauren web site):
However, I would think that for my body type, which is a bit ample in the hips and thighs, the plaid on the diagonal might look better. But the skirt shown below, with plaid on the diagonal, just doesn't look very appealing to me. What's wrong with it? Is it just really badly photographed? Is it the visual look of black and white plaid with black tights and black top? Is it badly made? Is it badly designed? Maybe it needs a waistband. I especially don't like the way the skirt appears to draw in below the hips and then hang in little drapes. Something is just wrong here and this is a look I do not want to create.
(Anne Klein skirt from Dillards web site)
Edited to add: Thank you Kathleen C. for your comments regarding the drape of fabric on the bias. It makes sense and I will keep it in mind when I attempt to make my plaid skirt!