Use commas after introductory words or phrases.
Subordinating conjunctions are words that connect, but unlike coordinating conjunctions, which connect equal parts, subordinating conjunctions connect dependent clauses (incomplete thoughts) to independent clauses. When you see a subordinating conjunction at the beginning of a sentence, this signals an introductory phrase, and you know a comma is coming at the end of that subordinate phrase, as illustrated in these examples:
Although they have stored a lot of food in their basement, I am not sure if they have enough for a zombie apocalypse.
Some of the most common subordinating conjunctions include the following:
I am not sure if they have enough for a zombie apocalypse, although they have stored a lot of food in their basement.
You should also place a comma after introductory words, as illustrated in this example: