So we've already discussed at length whether it's okay to start a sentence with a coordinating conjunction, and it's pretty clear that it is (and I've already done it in this sentence). But (there we go again) it's very common to start a sentence with a conjunction followed by a comma, like this:
So, here I go writing the first example.
This isn't limited to the beginning of a sentence. Although I've mostly seen it in the beginning of sentences, it's also common to see things like
I wrote the first example, and, then I wrote the second example.
The origin of this is pretty clear; it's the fact that we take often pause in such situations in spoken English, and people who see commas simply as punctuation sprinkled about to create pauses would never second guess putting a comma here.
It's my understanding that this is incorrect—that a comma should not follow a conjunction like this—but I don't have any definitive sources, so I wanted to make sure.
Best Answer
I don't know if it is flat out "incorrect", but I do know many style manuals recommend against it.
When I was young, the rule used to be that you are supposed to use a comma between phrases (before the conjunction, not after) if there are more than two things so conjoined. If it is only two, the comma is optional. I'd usually leave it off. You'd only put a comma after the conjunction if there also happens to be a subjunctive clause inserted there.
I had an occasion to look at a more recent style guide, and I believe it said the comma before the conjunction is always optional. I don't have any guide with me right now, sadly.