I mostly use Double "Quotations" marks when I am quoting something. I never really use single 'quotations' except when I'm editing some code that uses single quotes.
I think I saw someone who was british who used the 'single' qoutation for quoting. Lazy people or people who don't know much about North American grammer use 'single' instead of "double" when quoting.
I only use the ' when writing "it's , don't woudn't, can't etc."
well it happens some people are poorly educated in the way of the quotation and some are poorly educated in the way of the waffle iron it's a trade off thats worth while in some instances i suspect