Commas: Serial and transitional and interrupting, oh my!

Commas seem to be a real issue.  Apparently, at some point in elementary or junior high school, teachers mentioned using commas before the word "and."  It appears to me that the students who grew up to be lawyers took that very literally and every time their sentence has and, they want to put a comma.  "She went swimming, and splashed."  Commas are not easy and, again, I don't claim to know all the rules regarding commas.  I read the sentence to myself, taking out nonessential and interrupting phrases, to make sure the sentence still makes sense.  Other than that, I try not to use too many commas as I think they are really overused.  Here are some examples:

Nonessential expressions - commas set off words that are not essential to the meaning of the sentence.  "Brian Smith, the IT manager, was able to fix the computer."  When a you name a specific person, you don't need descriptive information to understand the sentence.  One way to determine if the expression is nonessential is whether your voice rises or falls on that part of the sentence when you read it.  If your voice drops, it is nonessential and should be set off by commas.  "We decided, nevertheless, to make plans to go to Spain."  If you voice rises, it is essential to the sentence and should not be set off.  "We nevertheless decided to make plans to go to Spain."  If, however, you mean only that you decided to make plans to go to Spain without any outside limitations in the rest of your paragraph, the nevertheless should be set off by commas.

Interrupting elements - commas set off words that break the flow of the sentence.  "He worked a long day, one of many lately, and left the office exhausted."

Transitional expressions - commas set off expressions that transition the sentence, such as however, therefore, on the other hand.  "On the other hand, Karen loves sushi as much as I do."

Afterthoughts - use commas to set off unrelated afterthoughts at the end of a sentence.  "He was late to work again that morning, if I remember correctly."

Serial commas - when a series of three or more items and the last item is preceded by and, or, or nor, a comma goes before the conjunction along with between other items.  "She ate steak, baked potato, steamed broccoli, and salad for dinner last night." People will argue forever with me on this one.  It is standard practice for some newspapers and magazines to leave the last comma out.  It can really lead to confusion, particularly in the legal field.  Using only two commas in a series could theoretically end up hurting someone.  Consider this example: 

John left his estate to Jack, Jill and Joe.  When taken literally, the estate would be divided into two parts - half to Jack and half to Jill and Joe to share.  If John had left his estate to Jack, Jill, and Joe, it is clear that the estate goes to three people.  Our business is extremely literal, so serial commas are important.  I will share a funny (although a tiny bit risque) picture going around Facebook recently on this very topic for the Grammar Giggle this week.  

We will share more about commas and move on to semicolons and colons in later issues of this blog.  I have to do much more research to blog intelligently about those topics -- there, I admitted it!  We will all learn through this process and for that I thank you.  It is important to constantly learn and I hope to share something worth learning each week.