Day 37: Only use one exclamation mark, if any.

Exclamation marks generally do not have a place in formal business writing, though they may have a use in advertising text and narrative texts. However, if you do decide to use an exclamation mark, only use one at a time. Strings of exclamation marks are characteristic of amateur writers, and most readers will interpret them as a ploy to create artificial enthusiasm. In either case, using more than one exclamation mark at a time will damage your professional image and credibility.

Improper use: “This is the best sale of the year!!!!”
Proper use: “This is the best sale of the year!”