Facebook had a couple of interesting questions/examples on "so." SO I thought it would be good to take a look at them. This is my answer to the questions about the word "so" in the FB sentence below.
...If, after a question has been posed to you, you have any question relating to what is being inquired about, please tell me before you answer the question. So just make sure you understand what you're answering before you answer it.
"So" is both a subordinate conjunction, which begins a dependent clause (which we are not discussing here), and a conjunctive adverb, which begins a brand-new sentence, that is, an independent clause. The sentence above that begins with "so" is an independent clause, not a dependent clause. It is a command form. Therefore, the word "so" has a period or a semicolon in front of it.
...The reporter's only able to transcribe audible responses, so things that can be heard.
In the example above, "things" is an appositive to "responses." The word "so" does not have a complete sentence after it even though it probably means "therefore." There is a comma in front of it.
...He arrived at 5:00; so he missed the meeting.
...He arrived at 5:00, so missed the meeting.
...I am out of the office today; so I will call you tomorrow.
...I am out of the office today, so will call you tomorrow.
Happy punctuating!
Margie