Automatically convert quotations in the form of "abc" to become ``abc"

An alternative to quotes is csquotes from 2011, while quotes is from 1997 …

\documentclass[english]{article}

\usepackage{babel}
\usepackage{csquotes}
\MakeOuterQuote{"}

\begin{document}
Hello "World"!
\end{document}

The package csquotes has many more goodies than the one mentioned. If you use the command \enquote{. . .}, you can nest several levels of quotations, while LaTeX preserves the correct couples of signs. You can even set localization preferences in order to use the proper signs for a language.

For instance, \enquote{\enquote{This is a quote within a quote}} will be rendered as:

“‘This is a quote within a quote’”

(with a thin space in between the contiguous signs).

But if you load the csquotes package thus (as I usually do):

\usepackage[autostyle=false, style=british]{csquotes}

the previous code will be rendered thus:

‘“This is a quote within a quote”’

See the documentation of the package for further details (texdoc csquotes).

There is a package for this: quotes. With this package, "text" is typeset correctly as ``text''.