We like to make all communications easy for viewers to read. And of course we never want to create stumbling blocks to their concentration and comprehension!
1  Avoid distracting “widows”, “rivers” and “orphans”.
Rivers are a series of word spaces on consecutive lines of type that align more or less one over the other to create the appearance of a visual river in the text. Rivers can be vertical, diagonal, or even curved. They can be hard to ignore and divert your reader’s eyes, competing for needless attention.
A widow is a single word alone on a line at the end of a paragraph.
Orphans are single lines of copy alone at the bottom or top of a page or column.

2  Optimal Type Alignment – Aligned Left, Right, Justified, or Centered?
Justified body copy creates more rivers, undesirable letter- and word-spacing and hyphenation issues. If you must justify, there are a few things you can do to minimize visual disturbances. Adjust the size of margin, decrease the body copy size, or manually hyphenate the text.
Right-aligned and centered are generally not used for body copy. Left-aligned text is just right!

3  Insert only a single space after all punctuation.
4  Avoid underlined text. In today’s world this is a visual cue that the text is a hyperlink. Emphasis can be achieved by using italic or bold.
5  Text longer than a short headline or subhead should never be in all caps. As a rule use upper/lowercase letters.
6  Increase line spacing to improve readability in body text.

7  Ensure sufficient color contrast between the type and its background.

8  Lines of type should not exceed 52 characters in length, or two alphabets. When lines are too long, readers may lose their place in returning to the next line.

9  For a single-column width – 4.25 inches is ideal and a two-column width can be as narrow as 2 inches.
10  Avoid letterspacing upper/lowercase copy.

11  Create a hierarchy of messaging with your type. Which one or two messages do you want to command the viewer’s attention? Vary their size and weight accordingly and direct the viewer’s eyes.

Read more about Visually Leading Your Viewers With Intent.
Keep these simple rules in your arsenal to ensure your copy is readable and have fun with type!