Here's a studio tip.
This full-length mirror is about 24 inches wide by 5 feet tall, made from heavy plate glass. I got it at a yard sale. I attached it to a plywood panel with a wood moulding around it. The whole panel is firmly screwed to the wall of the studio with a very strong piano hinge along the left-hand side. This allows the mirror to be swung out from the wall at any angle.
I use this mirror in two ways. First, since it is about ten feet behind my drawing table, I can look back to check the reflection of a work in progress. In this way I can quickly spot any flaws in the drawing, and I can see if the tonal organization carries from a long distance.
Before I hung it on the wall, I used to put a big mirror on an easel behind me, but I backed up into (and broke) a couple that way.
I also use the mirror for quick preliminary studies like this one, where I posed for a figure carrying a bunch of bananas (I was too lazy to get real models). I took the pose, studied the action, and established the basics. The American illustrator Tom Lovell suggested this idea to me.
Thanks, BoingBoing for doing a post yesterday about "My Friend the Cave Man," and thanks, Kyle, for telling me about it (I was literally staying in a log cabin in Ithaca cut off from everything for the last three days).