Q. When you start a sentence with so should it be followed by a comma? Example: So, let’s write one.

A. Because so serves different purposes, it’s not wise to make a rule that there should always or never be a comma after it. Try to hear the meaning in your sentence. If there’s a pause, consider using a comma while keeping in mind that other punctuation—or no punctuation—might make the meaning more clear than a comma.

So . . . let’s write one.
So! Let’s write one.
So—let’s write one.
So, let’s write one.
So let’s write one.