We do not generally put a comma before or after the adverb “never” to separate it from the verb it modifies. But use a comma to separate two instances of this word for emphasis.

We do not typically use a comma to separate the adverbs “frequently” or “infrequently” from the word they modify.

We do not generally use a comma before or after “hardly ever”, or “hardly”, to separate the adverb from the word it describes.

We usually place the adverbs “seldom” and “rarely” before the main verb (or after the verb “be”) with no comma before or after it.

In the middle or at the end of a sentence, we do not typically use a comma before or after “often”.

In the middle or at the end of a sentence, we do not typically use a comma before or after “occasionally” or “sporadically”. However, there are particular sentence constructions where commas may be used.

If a sentence is clear, the comma after an adverbial prepositional phrase at the beginning of a clause is optional. However, the longer the introductory phrase, the more likely you will place a comma after it.

At the beginning of a sentence, we usually put a comma after the introductory phrases “when in doubt”, “in case of doubt”, “beyond doubt”, etc.