While sketching in relaxed mode on paper is the best way, if you enjoy digital art, often you think "gracious me wouldn't it the greatest to just sit on the settee with my little Cintiq or Tablet PC and draw away". It seems like a dream proposition. But I have never found it very easy to produce decent results this way. Calibrate your screen as you may, you are never going to get your head or the device in exactly the same place twice - even from minute to minute.
I did a test where I tried to ink the same picture on the same computer screen, once on the settee, once sitting down at a desk. I made the pencils rough so I would have to make decisions about my inked lines, rather than just tracing the pencils. I find this a more interesting way to work all the time, not just when I am doing an experiment that may interest nobody at all. Working digitally gives me a lot more freedom in my inks, because I am not scared of making a mistake. Here are the results of this thrilling test-ette:
In the picture on the right, I blow a lot of lines, overshooting my mark, and I am plainly tracing rather than making decisions or trying to produce more attractive strokes. You can particularly see this in the feet, which I left very rough in the pencils. On the left, while the drawing isn't perfect, it's a lot better because I wasn't having to organise my actual physical body to keep everything in the right place.
The evidence is clear. We must all sit straight-backed and alert as we draw. Plus, laptops cook your conkers, fellas, and we have to keep the next generation safe. Adieu!