When you DO put a comma after a time order word:
* When it introduces a dependent clause: A dependent clause cannot stand alone as a sentence.
* Example: *First,* we will go to the park, and then we will go to the grocery store.
* When it introduces a list:
* Example: *Later,* we will eat pizza, play games, and watch a movie.
* When it creates a pause for clarity:
* Example: *Finally,* after a long wait, the train arrived.
When you DON'T put a comma after a time order word:
* When it introduces an independent clause: An independent clause can stand alone as a sentence.
* Example: *First* we will go to the park.
* Example: *Finally* the train arrived.
Key takeaway: Focus on the structure of your sentence and how the time order word functions. If it introduces a dependent clause or a list, use a comma. If it introduces an independent clause, you can omit the comma.