The first step is, in my opinion, the most important and as such can take the longest. It's the line work. This is the structural foundation on which you will build the rest of the image. It will guide and inform the entirety of the rest of the image.
I understand that to a lot of people lines are boring, but too many people get it 'good enough', and just rush in to the modeling of light and shadow. DON'T DO THAT! You will only succeed in lowering the overall quality of your work. I will admit this is something I struggle with myself, but trust me, if it takes you an extra hour to make sure that your lines are accurate, it will be an hour well spent. If you are working from a live model make sure that they don't need a break.
When shifting a line that you are otherwise pleased with it is a good idea to draw the new shifted line before erasing the old line so that you can use it as a contour guide. However if you are shifting a more complex element such as an eye or mouth you are probably better off completely erasing the original first and starting fresh.
Just draw lightly otherwise even if you erase you'll get subtle ghosting effects later when shading. Again this is something I sometimes struggle with as I like the aesthetic of heavy lines even though they are not really your friends at this step, and many people dislike them on lit edges.
In the next post I'll discuss highlights.






