For me, the comma has always been the most problematic of punctuation marks. As a newspaper reporter in the 1980s and 1990s, I was taught to leave out the Oxford comma because it represented an extra keystroke. And the Associated Press Stylebook, the Bible for journalists since 1953, considered extra keystrokes mindless waste.
Later, as a graduate student, I was taught to put the Oxford back in. Formal writing demanded a more formal presentation. That meant putting a comma after the penultimate item in a list of three or more items because to do otherwise was to invite confusion.
Some of the most heinous uses of the comma — or its non-use — are documented on the web site Mental Floss. My favorite — "This book is dedicated to my parents, Ayn Rand and God" — is particularly enlightening. Others examples are no less so.
For that reason, I use the comma in Oxford situations. But in other situations, I shy away from it. I don't like using commas after the first word in a sentence, before the last word in a sentence, or before a dependent clause. Grammatically correct or not, it looks funny.
I have a better grasp of other punctuation marks, but I use them less often because they are discouraged in fiction writing. Novelist Elmore Leonard, in his rules for writers, insists that no more than two or three exclamation marks should be used every 100,000 words. Many others believe the colon and semicolon should not be used at all.
Greats like James Joyce, Cormac McCarthy, and William Faulkner have taken a minimalist approach to all punctuation. I don't go that far. I view punctuation marks much like the words they regulate. They are tools. And like all tools, they should be used wisely.
