Here is a progress outline of how I painted a study/sketch/whatever you want to call it of my cousin's kid Emily. My camera broke down part way through, but I've put this step-by-step together so smoothly that you probably won't even notice where a dozen steps are missing.
Step 1: Start drybrushing to place the features.
Step 2: Succumb to boredom and dive into colour.
Step 3: Keep going in spite of your instincts.
Step 4: That's better.
Step 5: Once dry, go over it again.
Step 6: Out of curiosity I did something I tried on a project last year. I imported a photo of the painting into my computer and compared it to the original photo by overlaying them in Photoshop. I was doing this to see just how accurate my drawing was, considering I slacked on that part. I was surprised to find that the only real error was that her left eye was a little far out. See below for the correction.
Here's the face at the end of the orbital reconstruction:
Step 7: Now finish it.
Looking at the picture here, her colour is a little saccharine, although pretty colourful for a palette with only black, white, yellow, and red on it, plus a cameo from Transparent Red Oxide. I think I went wrong when I lost the half-tones in the cheeks, and also the whites of her eyes are a bit bright, but any darker and she didn't seem to be meeting your gaze anymore. The white was necessary, but it kind of destroys the naturalism. Actually I'm starting to feel revved up to do some more work on this painting.
I have a bit of a problem with how cherubic Emily looks here. For one thing, in real life she's fascinated with all creatures slimy and scaly. For another, in addition to being artistically inclined, she draws pretty manly subject matter. Her granddad likes to hunt and she was recently caught drawing a picture of a hanging moose quarter. Drawings don't get much manlier.