Thomas, J. E., Saxby, T. A., Jones, A. B., Carruthers, T. J. B., Abal, E. G., Dennison, W. C. (2006). Communicating science effectively: a practical handbook for integrating visual elements. IWA Publishing: London.
Design for Non-Designers, Michael Faber (video)
Color can be used to enhance a document or presentation, but it should be used sparingly and with an eye to the cultural associations of certain colors.
Whitespace can be just as important for visual communication as the content you are communicating. Make sure to leave adequate and consistent spaces around blocks of text and inside text boxes and table cells.
Long lines of text are hard to read. If your layout calls for wide columns, make sure to increase the size of the text and the spacing in between the lines.
Most publications should use one or two typefaces at most. Sans-serif typefaces (i.e., typefaces without decorative "feet") may look cleaner but are harder to read at small sizes. It is common to use a sans-serif typeface for headlines and a serif typeface for paragraph text, though it is a good idea to select the two carefully so that there is a contrast between the two and it is clear that they are different typefaces. To add more variety throughout the text, use different styles of the typefaces (e.g., bold, italic, narrow, small caps).
Left alignment is often assumed to be easier to read, but it produces a "ragged" right edge and thus looks less polished. Justified text (text that is aligned both on the left and right sides of the paragraph) may be harder to read and is likely to produce strange spacing and hyphenation issues in narrow columns. With either alignment, it may also be necessary to be creative about word placement to prevent "orphaned" words at the end of the paragraph (i.e., lines that only have a single word).
If you will be using images within your content, it is important to know a little bit about the different types of image files and how much detail those files need to have.
There are two basic types of images - raster and vector images. A raster image is like a photograph. The computer stores color information for each individual point in the photo, but that's basically all it knows about the image. Vector graphics, however, are more like equations that tell the computer how to paint the image. By storing the equations instead of just point-based color information, a vector image can easily change size and "resolution" without losing quality.
Image resolution is a measure of the amount of information that can be displayed in different environments. We talk a lot about screen resolution nowadays. For example, the laptop I'm using shows 1280 pixels across the width of the screen, which is about 11.25" wide. (This works out to almost 114 pixels per inch.) If I have a photograph that is 600 pixels wide but I try to zoom in so that it covers my whole screen, the computer will have to invent another 680 pixels of width for me. This is why raster images look blurry when we zoom in too close.
Resolution becomes more of a problem for printing, since people can't zoom in and out of an image once it has been printed. For printing, you should aim for a resolution of at least 300 dots per inch. In practice, this means that a 600 pixel image should never be stretched over more than 2 inches of paper. For another example: if you have a flyer and you want an image to cover the entire background, you will need an image that is at least 2550 x 3300 pixels.