\documentclass{article}

\usepackage{quotmark}

\begin{document}

First quote uses an environment:
\begin{qt}This is a quote.\end{qt} This isn't a quote.

The next quote uses a text-block command:
\tqt{This is a quote.} This isn't a quote.

Now for some nested quotes:

\tqt{Did she say \tqt{I am here}?} he asked.

\tqt{She said \tqt{where am I?}\,} he replied.

\tqt{He said to me \tqt{I am Harry \tqt{Mad} Hatter},} I said.

Paragraphs within the quotes are dealt with automatically:

\begin{qt}Dear Sir/Madam,

I am writing to inform you that I would like you to quote this
letter in your so-called \tqt{funny} article, which I don't find
the least bit amusing.

Yours etc\end{qt}

Back to unquoted text.

\end{document}