Proper punctuation makes a difference in your writing. Like spelling and grammar, the use of punctuation tells your reader whether you understand the rules of writing. It also helps your reader more fully understand your meaning, which can sometimes be lost in an impersonal email, for example. In addition, proper punctuation shows a level of professionalism that is expect in the workplace. While casual texting and emailing may abound, some forms of communication require careful attention to the basic rules of punctuation.
Use a comma after the introductory phrase that starts a sentence. For example, even if the phrase is short, put a comma after it. Before long, you'll be putting this comma in without having to think about it.
Set off any phrase which interrupts the flow of the sentence, whether it's big or small, with commas. Test whether you need to use commas by removing the phrase. If the sentence still makes sense, use the commas to set off the phrase. This sentence, like the first, has an phrase set off with commas. A phrase, often called a parenthetical phrase, that appears at the end of the sentence is also set off with a comma, as this phrase exemplifies.
Separate items in a series should be separated with commas. For example: Eggs, bacon, and hash browns. Wine, women, and song. Life, love, and laughter. Crosby, Stills, Nash, and Young. Some style guides, such as AP style, argue that the comma before the and is unnecessary - and they are also right. Certain style guides do not use the comma. Check with your teacher or editor to make sure you are using the correct format and put in or leave out that comma consistently.
Use a comma before complete sentences joined by a coordinating conjunction -- and, but, for, nor, or, so, yet. This comma frequently gets left out. Putting the comma in makes a sentence more readable, and any reader appreciates that. Leave it out and you have a run-on sentence, which makes the piece more difficult to read.
Use a semicolon to join complete sentences without a coordinating conjunction; the semicolon shows the end of one sentence and the beginning of the next. Semicolons are often followed by a connecting word or phrase; however, a connecting word or phrase is not necessary. Sentences joined with only a comma are called comma splices; they are among the most common errors that occur in writing. If you are not sure whether to use a comma or a semicolon, see if you can write the sentences as two separate sentences.
Use a colons when the sentence is introducing or presenting a list. For example: The teacher requested the following items from the students: answer sheets, pencils and test booklets. Colons also set off a part of the sentence that is being presented as an example, as in the preceding sentence.