Prospective clients will gauge your professionalism and ability to satisfy their needs by the way you handle subtle details like punctuation and spacing. Avoid hitting the space bar twice after periods at the ends of sentences, as this creates distracting gaps—especially noticeable with justified text. Likewise, avoid hitting the Enter or Return key twice after paragraphs, as this creates distracting horizontal bands of white space between paragraphs. Instead, use your Paragraph formatting command to add Space After equal to one and one-half lines of text.
Use the proper apostrophe symbol (') and open and closed quotation marks (", ") instead of typewriter-like foot (') and inch marks ("). Although your software may often automatically enter these appropriate punctuation, you should always double-check for accuracy. Instead of double-hyphens, use a typographically-correct Em dash (—) to indicate parenthetical expressions and shorter em dashes (–) to indicate duration and compound words.
Finally, use non-breaking spaces to avoid splitting proper nouns, cities and states and dates across two lines. In many cases, you'll have to edit, or transpose words, earlier in the paragraph to avoid awkward word breaks.