I started this off with an idea I had really late at night. This composition I thought of really resonated with me, and I felt like it reflected something of my personality. I took that first picture with my computer webcam, and although you can't see it, I had to reach my left arm under and across my right arm to hold my computer out far enough - it was quite the feat of contortion. The top of my head and most of my hand were cut off in this first picture, so later I had my brother take some versions that included my whole head. That's where the second two pictures came from. I did some cropping to get those to where I wanted them to be. Then I did some roundabout and inefficient photoshop magic to get evenly spaced grid lines (the rectangles make a 10x10 grid) and saved it. I liked the composition and angle of the second photo less, but the shadows and features were better, so I'll use that as a second reference photo to accentuate depth when I ink the details and hatching.
When it got to drawing the grid, I realized I didn't have a yardstick at home, and so I used a string taped to the table to mark points on the paper that I could then connect with a regular 1 foot ruler (credit to Raina for the idea). The drawing started off pretty well despite my doing it late at night. I find the 10x10 grid really helps with accuracy, because it lets me judge how far between two points a contour line intersects a gridline. I can mark those points and just connect them with the right curve in the line. The mouth currently is not at all accurate, so my next step is going to be to fix that.
While the 10x10 grid that I do is initially extremely difficult because of the precision and accuracy and math that I insist on, it makes the whole drawing process so much easier for me, and in my mind is totally worth it for the greater accuracy it gives me in copying an image. If I do it well, there shouldn't be any gap for judgement - it should always be clear where the "right" line should go, and if something is off, it should be clear in how it's wrong.