%!TEX TS-program = xelatex -output-driver="xdvipdfmx -v"
%!TEX encoding = UTF-8 Unicode

\documentclass[12pt]{book}
\usepackage{fontspec,xltxtra,xunicode}

\defaultfontfeatures{Mapping=tex-text}
\setmainfont{Times New Roman}

% Un/comment the following:
%\newfontfamily\zhfont{Apple LiSung} % Have to declare as don't have SimHei
%\usepackage{zhspacing}
%\zhspacing

\begin{document}
`It's hard to ‘say’ if ``it'' doesn’t like “fancy quotes”.'

\fontspec{STSong}

`It's hard to ‘say’ if ``it'' doesn’t like “fancy quotes”.'

\end{document}