Despite sharing a common English language, U.S. and British punctuation rules differ in ways we may not often realize. The British style has become more acceptable in the U.S. since many consider it more logical, but academic and professional writing in the U.S. still demands using the U.S. style. Having said that, a publisher’s style (often found in a style manual) may take precedence over a culture’s accepted rules. Consult your style manual for its requirements.
Quotation Marks
In the U.S. style, we use double quotation marks to indicate a direct quote and single quotation marks to set off a quote within a quote.
Ex. Brian’s dad always says, “Boys will be boys.” or Brian laughingly stated, “My dad always says, ‘Boys will be boys.’”
In the British style, the marks are often reversed, using single marks for primary quotes and double marks for quotes within quotes.
Ex. The sign read, ‘Please queue against the right wall only’. or ‘The woman just said, “Please queue against the right wall only”’, Hermione explained.
Periods and Commas
In the U.S. style, periods and commas come within closing quotation marks.
Ex. Taylor begged weakly, “Please don’t ground me; it’s the weekend.”
In the British style, periods and commas come outside closing quotation marks.
Ex. ‘The first step on the journey to success is to pick up one’s foot and move it’, my wisecrack teacher stated philosophically.
Ex. The constable ordered the biker, ‘Stay out of the bus lane, sir’.
http://www.uhv.edu/ac/newsletters/writing/grammartip2007.09.04.htm