The comma should come before the word "but" when it is used to separate two independent clauses. For example: "I wanted to go to the store, but it started raining."

Comma's are the hardest punctuation mark to place in a sentence. A comma can be placed after instead at the beginning of a sentence if the sentence is a continuation of the subject in the one before it.

In English, use a comma before someone's name when directly addressing them in a sentence or letter. For example: "John, could you please pass me the salt?"

True. Correct comma placement can help clarify the meaning of a sentence and prevent misunderstandings. Incorrect comma placement can alter the intended message of a sentence.

Typically, there is no need for a comma before the word "as." However, using one is not technically wrong, just superfluous.