The coordination of the series is a delicate, and almost controversial, subject; because it involves the ever sneaky use and placement of that dastardly little punctuation mark we call the comma. To coordinate the structure of a sentence using three or more components one must first use caution and become fully aware that there will be commas involved.
In academia, the rules are simple; a comma is always required when coordinating a series of three or more components. For example:
There are five different types of lettuce: Butterhead, Crisphead, Looseleaf, Romaine, and Celtuce.
Note that due to the excessive number of lettuce types, it is impossible to avoid using a comma when creating the series. However, if one wishes to be more specific when mentioning the various kinds of lettuce, and some of their unique characteristics, one could avoid the use of commas completely.
Butterhead and Crisphead types of lettuce have crisp leaves that form compact hearts.
Looseleaf and Romaine types grow best in cool weather and do not form significant hearts.
Although, commas are not as sneaky as they would have us think, they – unlike decent poker players – have a tell. The presence of an upcoming comma can be heard like an air raid siren if one knows what to listen for. In a series where three or more parallel coordinate elements are present, one can hear the slight change in pitch – the warning – that a comma is coming and then, there it is—the pause, the telltale sign that a comma has been used.
Nevertheless, beware the renegade! There are those who will omit the comma from the three-or-more rule in an attempt to dash those pesky smudges that dirty up a perfectly good piece of writing. They are the rebels of the literary world, the rule breakers, and the hoodlums, out to make a writer’s job even more complicated than it already is. But, do not be fooled lest your grades will suffer. Do not leave out the serial comma before the coordinating conjunction, it is but a trap.