Place a comma before these words only if what comes after could stand alone as a sentence (i.e., is an independent clause):
Smith is passionate about making music, and he is encouraging of his band members' individuality. [A comma is needed before and because He is encouraging of his band members' individuality could stand alone as a complete sentence.]
Smith is passionate about making music and is encouraging of his band members' individuality. [No comma; is encouraging of his band members' individuality is not a sentence.]
Smith is passionate about making music and encouraging his band members' individuality. [No comma; and encouraging his band members' individuality is not a sentence.]
Note: AAJ does not use serial ("Oxford") commas before the last and or or in a list (as shown in this section's title).
Information that isn't essential to the meaning of the sentence (i.e., is nonrestrictive) should come after a comma. If nonessential information occurs in the middle of a sentence, it should be placed between two commas:
"Smith's 2012 release, Untitled (Anomia Music), was critically acclaimed" indicates that Smith only had one release that year, and the sentence would still make sense if the extra information between the commas were removed.
"Smith's 2012 release Untitled (Anomia Music) was critically acclaimed" indicates that a particular album out of Smith's multiple releases that year is being discussed. In this case, if the name of the album were removed, the reader wouldn't know which of Smith's 2012 albums was being described.
Likewise, the comma in "Smith's wife, Mary" indicates that the name Mary is extra information that's just another way to describe Smith's wife. With no comma, "Smith's wife Mary" indicates that Smith has more than one wife, but Mary is the one being discussed.
Use periods or semicolons--not commas--between two sentences (or add a comma and a coordinating conjunction such as and, but, or, so or yet ):
He'd seen it all before, he knew what was coming. [Avoid comma splices like this one; it's often considered bad form to join sentences with commas.] He'd seen it all before; he knew what was coming. He'd seen it all before, and he knew what was coming.
Anything that comes after a semicolon should be able to stand alone as a complete sentence. If what you have is a sentence fragment, use a comma, em dash (by typing two hyphens --) or colon instead. (Exception: semicolons can be used instead of commas to separate items in long, complicated lists.)
Hyphenate compound modifiers only if they come before the noun they describe: "A well-known theremin player" indicates a theremin player who's well known. [Well known gets hyphenated only when it comes before theremin player, the noun it describes. Without the hyphen, a well known theremin player indicates a known musician who's well (as opposed to ill). High-school students [Without the hyphen, this indicates school students that are high.] or students in high school
Use double quotes for quoted material and single quotes for internal quotes within quotes.
Non-quoted material should be placed in brackets.
Be sure to place a comma or colon before the opening quotation mark.
Be sure to place periods and commas before the closing quotation mark.
Place question and excalmation marks before the closing quotation mark if they're part of the quote and use them instead of (not in addition to) periods or commas.
Smith explains, "Jane [Doe, lutenist and bandleader] wants to hear beforehand what I'm going to play: 'Yeah, yeah, do that; that's OK.' And I ask, 'What are you going to do?' And she just says, 'We'll see!' [laughs]"
Watch out for "dangling" modifiers that are missing their subjects, especially when starting sentences with a word ending in -ing:
Living in New York but born in California, Smith's eponymous recording received great critical acclaim. [As written, Smith's recording is what's living in New York, etc. Rewrite so that Smith is the subject: Living in New York but born in California, Smith received great critical acclaim for his self-titled recording.
Note: in this example, the word eponymous is used incorrectly. It does not mean "self-titled"; it is used to describe a person for whom something is named. So Smith is eponymous because an album is named for him, but his album isn't.]
Listening to their recordings, the band's changing aesthetic is unmistakable. [As written, the band's aesthetic is doing the listening.]