Klaus and Wilhelm Umlaut's Guide to Basic Grammar*

Dialogue

Dialogue is far and away the thing that gives people the most trouble. The most important thing to remember is that the period is not necessarily your friend. Whenever you have part of a line of dialogue followed by a tag such as "he said" or "she cried" or "he expostulated," be very careful what punctuation you use inside the quotation marks. In general, you want to use a comma instead of a period. Question marks and exclamation points remain the same. The first letter of the tag is not capitalized, unless it is a proper noun.

Examples:

Wrong: "I'm happy to be here." Reginald said. "This place sure is swell."
Wrong: "What do you mean?" Cried Sally. "The yak was here a minute ago."
Wrong: "Aiyee!" Expostulated Dirk. "Your Pomeranian has chewed my slippers!"

Right: "I'm happy to be here," Reginald said. "This place sure is swell."
Right: "What do you mean?" cried Sally. "The yak was here a minute ago."
Right: "Aiyee!" expostulated Dirk. "Your Pomeranian has chewed my slippers!"

As a sidenote, periods and commas always go inside the quotation marks. Question marks and exclamation points almost always do so, as well.

If Character A is directly quoting something Character B has said, Character B's words go in single quotes (in American usage, at least). This is usually only necessary if Character A is really stressing Character B's exact words. More casual quotation need not be set off from the rest of the dialogue.

Example

"Dudley said that Morton was 'a big stupid doofus who wouldn't recognize genius if it bit him in the spleen' when we were at the meeting yesterday," Drucilla explained.

That's about all the guidance most people need. But those interested in some of the finer details may wish to continue reading.

Oh, fine, just leave me here, in the insufficient lighting. I'll probably go blind from the squinting, but never you mind, you just have fun with your little friends.

The Hyphen: Descriptions

The general rule for multi-word descriptions is to hyphenate them if they come before the noun they describe, but not if they come after it.

Examples

The llama standing before them was badly mussed.
The mile-high llama devoured Los Angeles.
This is not an infallible rule, but is most often true. In the first example, "badly" functions as an adverb modifying the adjective "mussed." In the second example, "mile-high" works together as a single adjective, modifying "llama."

The Comma: Restrictive and Nonrestrictive Phrases

Consider these examples:
Zelda's brother Osric went to the fair.
Zelda's brother, Osric, went to the fair.
Which one is correct depends on the circumstances. In the first example, "Osric" is restrictive; i.e., Zelda has more than one brother, and "Osric" tells us which specific brother went to the fair. It restricts us to one brother. No commas are used here, because this is necessary information.

The second example is nonrestrictive. In this case we have to be talking about Osric because he's the only brother Zelda has. His name is additional information not necessary to the meaning of the sentence, so it is placed in commas.

Examples

Dwayne the Grand Pooh-Bah demands some taffy.
(We have never heard of Dwayne before, and need to know why he is significant. He is different from Dwayne the cost accountant.)

Dwayne, the Grand Pooh-Bah, demands some taffy.
(We have been previously introduced to Dwayne. The inclusion of his title is additional information)

This has been paraprhased somewhat, as the Umlaut brothers' original guide contained rather more threats and, on occasion, utterly disgusting pleading than was really proper. Or indeed legal, in some cases. They have said that they are very sorry, and will endeavor to do better in the future.

Back whence you came.