Avoid Orphans and Widows!
Orphan is a term used to describe a single word appearing at the bottom of a paragraph or column. A widow is a single word or short phrase appearing alone at the top of column. They add "rivers" of white space and interfere with eye movement from one line of text to the next.
You should also avoid putting less than three lines of a new paragraph at the bottom of a column. Fewer than three lines will make it harder for the reader to keep information organized. The example below demonstrates all three points.
White space can be under-used, overused, or just carelessly used. Good control of white space can improve reader comprehension. For instance, too much space between a column of text and a new subhead can interrupt the eye movement of your readers. Generally speaking, it's easier for people to read quickly if the spacing between words and lines isn't too lose.
Also, pay close attention to the space between paragraphs. If you indent the first line of text, then don't insert extra spaces between paragraphs. Do one or the other. Magazines generally indent and minimize space between paragraphs. Some newsletter designers use block paragraphs and add space between them.