The easiest way to start thinking about punctuation within clauses, as opposed to punctuating between clauses, is to consider where punctuation marks can’t go.
Not between Backbone Elements
We can’t put commas between subjects and finite verbs, between finite verbs and their completers, or between double completers (which are also called indirect and direct objects). None of the commas in the following two examples is possible:
ERROR: Only a very dumb frog, would retrieve, a golden ball from the piranha tank.
ERROR: She knew, Jumbo would probably forget, that he had a rumba lesson that afternoon.
The rule holds even when we feel a distinct pause between backbone elements, as in the following examples:
The only way I can think of to keep Fang from getting at the cookies [pause but no comma] would be to store them in the vault. [The structural backbone is way…would be.]
We are pleased to inform you [pause] that your boa has been thoroughly cleaned. [No punctuation is possible after you; you and the “that” clause are double completers of to inform.]
Not Directly after Connectives
We can’t put commas directly after connectives. This rule goes for all connectives: coordinating, non-coordinating, and marginal:
ERROR: I always tell Fang elephant jokes, and, Fang never gets them. [The comma after jokes is correct since it indicates the boundary between independent clauses, but the one after and is an error.
ERROR: It’s OK to lick your salamander, but, don’t sit on your egg salad sandwich. [The comma after but isn’t possible.].
ERROR: I don’t trust bedbugs, for, they’re attracted to tasty people. [The comma after for, isn’t correct.]
ERROR: He’s disqualified because, he insulted the salamander. [No comma is possible after because, a subordinating connective.]
Actually, a more common error is placing a comma after a coordinating connective while leaving out the one before it:
He serenaded Ms Beebs half the evening but, he forgot to tune his guitar.
Not between Coordinate Words Joined by Coordinating Connectives
We can’t place commas between coordinate words or phrases that are joined by coordinating connectives. None of the commas in the following examples is correct:
ERROR: Jack, and Jill went up the social ladder.
ERROR: He huffed, and puffed.
ERROR: You’ll find Fang either in the cookie jar, or over the rainbow.
Not between Adjectives and Following Nouns
A comma can’t come between an adjective and the noun that immediately follows it. We couldn’t, for instance, write white, paper ; vegetarian, cuisine; frisky, koalas; or sour, grapes.