As a general rule, add a comma after introductory phrases, like “in this instance”, “in every instance”, “in the first instance”, “at the instance of...”, etc.

At the beginning of a sentence, you can optionally add a comma after the phrases “under these circumstances”, “under any circumstances”, “in no circumstances”, “under certain circumstances”, etc.

At the start of a sentence, you can optionally add a comma after a prepositional phrase, such as “in this case”, “in any case”, “in some cases”, “in a large number of cases”, etc.

At the start of a sentence, you can optionally add a comma after a prepositional phrase, such as “in some situations”, “in this situation”, “in a variety of situations”, “in a range of situations”, etc.

At the start of a sentence, adding a comma after a brief prepositional phrase, such as “until now”, “until then”, “up until now”, or “until recently” is usually optional.

At the beginning of a sentence, using a comma after the expressions “for now”, “for years now”, “for the moment”, etc. is optional.

At the beginning of a sentence, we do not need to place a comma after short adverbial phrases, like “in the interim”. Longer introductory phrases (more than four words), such as “in the course of...”, are commonly followed by a comma.

At the start of a sentence, use a comma after prepositional phrases introduced by "at the time of", "at the time when", or "in the time of".

We do not typically use a comma before or after an adverbial phrase, such as “at the same time” or “for the time being”, to separate the phrase from the verb it describes.