The dreaded comma, tricky but not impossible to understand.
Besides what Terisa Folaron points out here; Conjunctions (FANBOYS) and Subordinates, there are few more important points to consider when using or not using the comma.
Misconceptions about Commas
#1 – You should add a comma wherever you pause.
Every reader pauses in different places.Where you pause or breathe in a sentence may not be where the reader needs a comma.
#2 -The rules are too confusing and I’ll never learn!
The rules are pretty clear. Some rules are flexible, but most of the time, commas belong in very predictable places. There are a few confusing debates on how to use a comma. (See below) But for the most part you can learn all the rules quickly!
The Oxford Comma:
The biggest discrepancy in using a comma is on how to use it in a series. Let’s look at an example:
William likes bread, peanut butter and jelly.
or
William likes bread, peanut butter, and jelly.
One may argue that while William likes peanut butter and jelly, he does not like them together. The other argument is that it is clear regardless and a comma is not needed.
A few other comma topics:
Introductory words, phrases, or clauses
Conjunctive Adverbs
Interrupters
Series
Describers
These all have important roles in comma placement. Are they difficult to learn? Not really. Find a good grammar book or teacher and practice. You will find that in a short period of time that you understand and feel a lot more confident in your English writing abilities,