If a sentence starts with an if-clause, add a comma after the if-clause. Do not use a comma when the sentence starts with the main clause.

In the middle of a sentence, we normally use commas to set off the word "too". It is not necessary to place a comma before "too" at the end of a sentence.

The expression "on the other hand" should be followed by a comma at the start of a sentence and surrounded by commas in mid-sentence.

Wherever the expression "by the way" comes (at the start, in mid-sentence, or at the end of a sentence), it must be separated by commas or other proper punctuation marks, such as a period, a semicolon, or an em dash.

When interrupting the sentence flow, use a comma before and after the expression "after all" in the middle of a sentence. At the start of a sentence, "after all" must be followed by a comma when meaning "despite that" or "because".

Expressions and words that interrupt the sentence flow, like however, nevetherless, or though, must be surrounded by commas in mid-sentence.

Add a comma after the words well, why, hello, and hey to introduce a new sentence. Alternatively, you can use an exclamation mark to show emphasis, emotion, or surprise. An exclamation mark after these introductory words replaces a comma.

Place a comma before "including" when introducing an example (or a series of examples) to illustrate what has been recently said.

Use a comma before and after for example and for instance in the middle of a sentence. Replace the first comma by a semicolon to introduce a complete sentence with these expressions.