I write a lot. I always have, and somewhere along the line I think I became halfway decent at it. Below are some of my thoughts on punctuation, with a few links to recent posts I've read discussing similar issues.
SEPERATING PHRASES
The Comma. A comma seperates clauses or items in a list. It is often optional[,] and should be used sparingly. Strategically, a comma is used in order to break the flow of a sentence. The comma before a conjunction at the end of a series -- i.e. "A, B, C and D" or "A, B, C, and D" -- is called the serial comma, oxford comma, or harvard comma, and (as with any comma that precedes a conjunction) it is a matter of taste. (See Wayne Scheiss' Legal Writing Blog).
The Em-Dash. An em dash (a long line, or two hyphens) can be used in lieu of a comma in any situation other than a list. It signals a long pause, and usually denotes that thought that is tangential to the rest of the sentence. (See Disputed Issues Blog). One of the most useful times to use an em-dash is when you want to set apart a phrase that contains additional punctuation, such as the example in the comma section above. When used at the end of a sentence, only one dash is used -- such as this sentence, here. As a practical point, the dash should be used very selectively. It makes a dramatic point, and tends to make a phrase stand out for the reader, but overuse can make your writing difficult to follow. As a rule of thumb, I never use more than one dashed phrase in the same paragraph, and I try to use no more than one such phrase every few pages.
Parentheses. Like the em-dash, parentheses can be used in lieu of a comma, particularly where the thought is a departure from the main point of the sentence. (As an aside, one of the interesting things about parentheses is that they can contain entire sentences, and even multiple sentences. When a parentheses contains a complete sentence, the period goes within the parens.) Parentheses can be used more liberally than the em dash, but should still not be overused.
COMBING WORDS
Hyphenation. Although many people would disagree with this, hyphenation is often merely a matter of taste. Hyphen usage is more common in British writing than American, and the overall trend is towards more sparse usage. A hyphen links two words so that they are viewed as a single concept, and thus can have a dramatic effect on readability. There are three reasons to use a hyphen: first, numbers, such as twenty-two or one-hundred, can be hyphenated; second, pre-fixes can by hyphenated to prevent mispronunciation or where the prefix/root combination is not common; and, third, hyphens can be used to combine words to create a stronger connection between them. A hanging hyphen is used for phrases such as one- or two-family home. (See Wikipedia)
The Slash. The jury is still out on the slash for me. A slash is often considered informal because of its use in abbreviations, such as w/. The slash, also called a virgule, can be use to instead of a prepositional phrase where the preposition would take two objects. Rather than saying "the X of A and B" or "the X between A and B," you can say "the A/B X." The phrase "prefix/root" in the preceding paragraph is one example. This device can be useful where you are discussing multiple contracts. I despite the phrase "and/or." Only the word "or" is necessary in most situations, and if you really want to emphasize that it could be both, you can say "A or B, or both." Similarly, "s/he" can easily be replaced by the plural.
THE COLON AND SEMI-COLON
The Colon. A colon says: here read this! It can be used to introduce a list, to denote speach, or to set off a single word or sperate phrase at the end of a sentence.
The Semi-Colon. The semi-colon is used to seperate independent clauses (that have their own subject and predicate). Some people claim it is under-used; but take caution, it can be habit forming. (See Disputed Issues Blog).
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