Some years ago I read that Jane Bown, legendary newsie/portraitist, used to evaluate the light by holding up her fist.
This works marvelously well. Your fist is not a face, but it has lumps and planes and pointy bits and protuberances. You can get an instant evaluation of the character of the available light if you simply hoist the thing up and really look at it. Make a fist, hold it up thumb toward your nose, and really stare at it a second.
I did some pictures of kids for a friend recently. City hall in town here has this big lobby area, with some large glass-brick panels in the face of the building, which faces due south. It might not be your classic North Light but with the glass brick it's pretty damned nice. I threw up my fist, got the feel of it, and away we went. I mean, it's 99% rapport with kids and 1% photography, but still.