A French Girl's Trick to Getting Dressed

Last year, I posted an outfit shot of me in a mini dress and high heels. It's my go-to combination in an effort to create the illusion that my legs are much longer than they actually are (I have a disproportionately long torso). A French reader left a comment about her rule of thumb when wearing a skirt or dress that I thought was genius. Lamimine wrote: "Lovely dress! I feel like it would be prettier with flats though. I usually go with flats when skirt is above the knee, and heels with longer length. French rule :-)." Though I usually follow a different equation (the looser the item, the higher the heel), I'm compelled to give the French route a go. What rule, if any, do you follow when getting dressed in the morning?