How to Generally Increase the Size and Line Spacing of the Footnotes?

I think that the footnotes are generally a little too small, and I would like to increase their size globally (for the entire document). How do I go about doing this?

Moreover, I think that the spacing between footnotes, and the line spacing for footnotes generally, is too small. How can I configure these (two different) properties of footnotes?

Here is the MWE:

\documentclass[12pt]{article}
\usepackage[margin=1in]{geometry}

\makeatletter
\renewcommand\@makefntext[1]{\leftskip=0em\hskip-0em\@makefnmark#1}
\makeatother

\begin{document}
Caesar non supra grammaticos\footnote{''even Caesar is not above grammar/grammarians.''}. Tu enim Caesar civitatem dare potes hominibus, verbis non potes.\footnote{This is going to be a longer footnote: ''Caesar, you can grant citizenship to men but not to words.''}
\end{document}


The default document classes define \@footnotetext to include a font switch \footnotesize. Here's a typical view on that:

You could use etoolbox to patch \@footnotetext and insert the appropriate font specifications as a replacement. Just add the following to your document preamble:

\usepackage{etoolbox}% http://ctan.org/pkg/etoolbox
\makeatletter
\patchcmd{\@footnotetext}% <cmd>
{\footnotesize}% <search>
{\scriptsize}% <replace>
{}{}% <success><failure>
\makeatother


The above replaces \footnotesize with the declaration/switch \scriptsize (you can pick your flavour). If you wish to space things out as well, use the setspace package to do something similar:

\usepackage{setspace,etoolbox}% http://ctan.org/pkg/{setspace,etoolbox}
\makeatletter
\patchcmd{\@footnotetext}% <cmd>
{\footnotesize}% <search>
{\scriptsize\setstretch{1.5}}% <replace>
{}{}% <success><failure>
\makeatother


For font size referencing, see How to change font size mid document?. For a setspace reference, see Why is the \linespread factor as it is?.