There are some typographical rules when it comes to dashes, following or violating them can be easily spotted and is often used as first indicator for typographical sloppiness. While there are many different dashes, I only want to focus on the most common ones: hyphen, en-dash and em-dash. The em-dash is often misused for a comma and overused “Dashes surround a series punctuated by commas: ‘The governor will face many problems—unemployment, declining revenue and rising costs—in the election year.’ Also use dash to mark an abrupt change in continuity of expression: ‘The balance of payments is—but you know all that.’ … Do not use a dash alongside a comma, a semicolon or a colon. … Avoid  dashes in headlines because they are ungainly in large type” (source: NYT Manual on Style and Usage). An em dash is ASCI character 151, so Alt+0151 (on the numeric keypad) inserts it. If its not available in your program, for instance in ASCII email messages, it is common to use to two hyphens. The en-dash is also called the figure dash because it is used between numbers, like in phone number 724-934-0706 or to denote numerical ranges. If not available you can use a hyphen or a minus sign instead. The hyphen is used for hyphenation—I guess you would have figured that—but, it can also be used between numbers in cases when an en-dash is not available and to hyphenate compound words. The em-dash or m-dash has the width or the lower case “m” and the en-dash or n-dash has respectively the width of the lower case “n.” The en-dash is wider than a hyphen. There should be no spaces before and after an em-dash.