I look at the face of the plug, to see where the plastic bit is in the plug. By spec, that should be on the bottom. (The spec is the trident icon on the plug should be up, but the trident icon doesn't show up well.)
I found the spec section, Sec 6.5.1 USB Icon Location, that says "Receptacles should be oriented to allow the Icon on the plug to be visible during the mating process." For horizontal ports, that means up. For vertical ports, all best are off.
That's also not stopped ID departments from designing enclosures where the motherboard went in upsidedown, so the motherboard connectors were upside down once it was in the enclosure. We didn't notice that when we only had boards to work with, once it was in an enclosure it was too late to fix it.