Alignment – Alignment refers to positioning elements flush with a grid or each other. Ins ome graphics software apps you can create a grid or guides on a layer to aid in alignment and then hide that layer before printing.
Contrast – Contrast refers to the contrast of text to background and legibility. If the color and contrast ratio of text to background is too similar people with visual disabilities may have difficulty reading it. Good contrast allows designs to be legible in either color or black & white printing.
Proximity – The proximity of elements is used to group related information together in visual communication. The proximity of elements to each other shouldn’t be too close, in many cases use of more white-space and padding creates a cleaner looking design.