I believe the double quotes is what you would use normally. You can use the single quotes to show a quotation within another quotation. The single quotes are not often used. I see them more often used in programming languages where single quotes show a single character, and double quotes show a string of characters.

the usage of Single Quotation Marks ' ' and Double Quotation Marks " " Double quotation marks can also be used to: 1- indicate that a word is special in some way. 2- when you are writing a sentence and you want to refer to a word rather than use its meaning. The most common use of single quote is : 1- when you are quoting someone who is quoting someone else. You enclose the primary speaker's comments in double quotation marks, and then you enclose the thing they are quoting in single quotation marks. http://grammar.quickanddirtytips.com/single-quotes-versus-double-quotes.aspx