Where in a sentence does comma needed?

You're asking a very interesting question! There's no single spot in a sentence where a comma *always* goes. It depends on the specific elements of the sentence.

Here are some common uses of commas:

* Separating items in a list: "I brought apples, bananas, and oranges to the picnic."

* Joining two independent clauses: "The sun was shining, but the wind was cold."

* Setting off introductory phrases: "After a long day, I was exhausted."

* Setting off non-essential clauses or phrases: "The book, which I read last week, was fascinating."

* After a direct address: "John, can you please pass the salt?"

* After a dependent clause that comes before an independent clause: "Because it was raining, we stayed inside."

Important Note: Punctuation rules can be complex. If you are unsure about where to put a comma, it's always best to consult a grammar guide or online resource.