COORDINATING CONJUNCTIONS (A comma precedes a coordinating conjunction that separates two independent clauses--complete sentences.) Preferably, a writer should not begin a sentence with a coordinating conjunction. An easy way to remember these conjuctions is to learn that the first letter of each one spells out FANBOYS.
CONJUNCTIVE ADVERBS a.k.a. ADVERBIAL CONNECTIVES, LOGICAL CONNECTIVES AND SENTENCE ADVERBS (A semicolon separates two independent clauses that are connected by a conjunctive adverb; usually a comma follows the adverb.) If these conjunctive adverbs serve as sentence interrupters, they should be set off from the sentence with commas.
accordingly, in fact, on the other hand, besides, later, otherwise, consequently, moreover, perhaps, finally, nevertheless, still, furthermore, next, then, however, nonetheless, therefore, indeed, and now
SUBORDINATING CONJUNCTIONS (These connect dependent or subordinate clauses with independent clauses.) NOTE: a subordinate clause without an independent clause is a fragment.
The following conjunctions introduce adverb clauses:
(Introductory adverb clauses should be followed by a comma.)
after, because, so, that, whenever, although, before, though, while, as, even though, till, wherever, as if, if unless, whereas, as long as, in order that, until, as soon as, since, and when
The following conjunctions can introduce adjective clauses:
(Punctuation is determined by whether the clause is essential or non-essential.)
when,which*, where, whoever, why, whomever, who*, whose*, whom*, and that*
*Also known as relative pronouns
The following conjunctions can introduce noun clauses (No comma(s) required):
where, what, why, whatever, how, whoever, who, whomever, whom, that, and whose
either . . . or
neither . . . nor
not only . . . but also
both . . . and
whether . . . or