They say that art mirrors life. In the toolkit of every good artist is a mirror as well. For the graphic artist, the mirror may be real rather than figurative.
As part of a larger project, I've assembled three cartoon characters I've designed. Knowing that there's a good probability that the characters may face camera left or camera right, I digitally flipped the images.
This is an important step. By mirroring the image, we can see flaws that are generated by handedness. A right handed artist will tend to have lines curve more naturally one way, while a left handed artist draws curves the other, following the natural motion of the wrist while drawing. Flipping the image allows the artist to draw from both sides.
If working on paper, the artist can simply rotate the paper to see a new perspective. Also, you can flip it by holding the drawing up to a strong light and by looking at the lines through the paper. On larger pieces or paintings, the artist will use a real mirror. Archival evidence points to some ingenious mirror systems used by some of the great painting Masters.
Finally, digital art tools like Photoshop allow us to easily flip an image, as seen above. Photoshop is also good for flipping photography. Photographic elements can also be affected by handedness, so sometimes I will flip perfectly good photos just to enliven the composition.