Becky Burckmyer, author of Awesome Grammar (Career Press, 2008, shares the “top 10” grammar errors she has seen in her 20-year career as a copywriter, writing coach and seminar leader:
1. Incorrect placement of quotation marks. Note that quotation marks go OUTside periods and commas, whether the little marks are part of the quoted material or not:
Archie has written a song, “Green Christmas,” which I think you should hear.
All other punctuation goes inside or outside depending on whether it’s part of the quotation. If this rule seems odd or unfamiliar, you may have been reading material published in England, where periods and commas, like all other punctuation, American or British, are in if they’re part of the quoted material, out if they aren’t.