Whenever we have to use a question mark or an exclamation point with a sentence that ends in a quotation, we follow the dictates of logic in determining where the question mark or exclamation point goes. If it is part of the quotation itself, we put it inside the quotation marks, and if it governs the sentence as a whole but not the material being quoted, we put it outside the quotation marks.
• Have you read the assigned short story, “Flowering Judas”?
• No, but I did finally get around to reading last week’s assignment, “Where Are They Now?”
When it comes to commas and periods, though, logic doesn’t enter into the equation, at least not in the United States. Universal American usage places commas and periods inside the quotation marks, regardless of logic.
• “Diane,” she said, “put the book down and go outside for a little while.”
• “I will in a minute,” she replied, “as soon as I finish this chapter.”
This rule applies even when the unit enclosed at the end of the sentence is just a single word rather than an actual quotation:
• To get to the next page, just press the little button marked “Enter.”
The only exception is when that last little item enclosed in quotation marks is just a letter or a number, in which case the period or comma will go outside the closing quotation marks:
• The buried treasure was marked on the map with a large “X”.
• The only grade that will satisfy her is an “A”.
• On this scale, the highest ranking is a “1”, not a “10”.
Of course, if another set of words or a parenthetical citation gets between the quoted material and the end of a sentence, then the comma or period will follow the intervening elements:
• “Diane, put the book down and go outside” was what her mother said, but what Diane heard was “Blahblahblahblah” or something even less meaningful.
• The question is whether the persona is expressing a death wish in those identical final lines, “And miles to go before I sleep, / And miles to go before I sleep” (15-16).
Now, keep in mind that this comma and period inside the quotation marks business is strictly American usage. The British don’t do it that way. They are inclined to place commas and periods logically rather than conventionally, depending on whether the punctuation belongs to the quotation or to the sentence that contains the quotation, just as we do with question marks and exclamation points.
My American students, though, don’t get to choose. They have to do it the American way, just as they have to drive on the right side of the street, even though the British drive on the left side. (Of course, the British also drive on the right side when they are in this country, so maybe that’s not such a good comparison.)
Anyway, the point is that if you are an American, you need to keep your commas and periods inside your closing quotation marks, where they belong.*
And just why, you may ask, do they belong there? Well, it seems to be the result of historical accident. When type was handset, a period or comma outside of quotation marks at the end of a sentence tended to get knocked out of position, so the printers tucked the little devils inside the quotation marks to keep them safe and out of trouble. But apparently only American printers were more attached to convenience than logic, since British printers continued to risk the misalignment of their periods and commas.
More grammer help from Tina Blue: http://grammartips.homestead.com/inside.html