I am always fascinated by and questioning grammar.
But my current ESL (English as Second Language) student, Naomi, raises the bar and thankfully forces me to take a second look at what I know -- and what I think I know.
One of her ongoing questions is about commas and introductory words and phrases. She wants to know: if my sentence begins with "Then," is it always followed by a comma?
So I was very excited (in only the way that grammar geeks can be) when I saw this recent Q&A posted on the Chicago Manual of Style list:
Q. Is it necessary to use a comma after words like next, then, after that, last, and finally when they are the beginning of a sentence?
A. Punctuation is not so simple that you can make a rule that a comma “always” follows a given word or phrase. Commas depend on syntax as well as pacing, tone, and personal preference. Two examples with next:
Next comes the scene where he buries the toenails.
Next, since he was still breathing, she worked a crossword puzzle.
So, there are no rules all the time.
How many times have I said to Naomi (and myself, for that matter):
"When in doubt, do you hear a pause? If you do, then you probably need that comma."
That "natural language" response will usually help you in deciding "comma or no comma." Trust your voice, and trust the language you've learned.
Listen for those little pauses after those little words. And listen for those little commas.