Christian J. Robinson: Punctuation/Spelling Rant

People misunderstand the proper use of apostrophes. The worst is "it's" versus "its". If you simply remember that "it's" is always a contraction ("it is") and "its" is for possession ("the flower lost its petal"), you'll be fine. For more information on how to use the apostrophe properly, learn from Bob the Angry Flower and The Apostrophe Protection Society.

When you end a sentence as an exclamation, one exclamation point ("!") is sufficient to convey the idea of strong feeling or emphasis. Three is sometimes used for extreme stress but no more than that, and it's considered unnecessary and tacky. You never end an exclaimed question with "?!"/"!?", only an exclamation point is used. And you never use more than one question mark.

When you omit part of a thought, the triple-dot or "ellipsis" ("...") is used, and four are always used at the end of a sentence—never more than that, never less. When you end a sentence with an acronym or an abbreviation you never end up with two successive periods, one is dropped ("etc." not "etc..", "T.L.A." or "TLA." not "T.L.A..")

Punctuation always goes inside quotes. All of these are all incorrect:
"This is wrong".
He asked "is this right?".
He said "I guess not", and shrugged.

Although I will sometimes deliberately break this rule when I feel clarity is necessary, as seen above.

These mistakes are especially prevalent online.