How do I change the way section headings look? [duplicate]

I have a few sections in my document that look like

\section*{Introduction}


The font size seems slightly too big for me, and I would like to make it smaller. I found the following \renewcommand snippet (link here):

\renewcommand{\section}{\@startsection
{section}%                      %the name
{1}%                            %the level
{0mm}%                          %the indent
{-\baselineskip}%               %the before skip
{0.5\baselineskip}%             %the after skip
{\normalfont\large\itshape}}%   %the style


But I get the error

You can't use \spacefactor' in vertical mode

How would I go about solving this problem?

Thank you,

• – egreg Jan 8 '13 at 22:00
• @egreg I don't understand how your link relates to my question here. Could you be more specific? – cartonn Jan 8 '13 at 22:04
• The command \@startsection you're using has @ in its name; that thread addresses precisely this problem: put \makeatletter before and \makeatother` after that code. – egreg Jan 8 '13 at 22:07
• Thank you, it works now. I'll accept your answer if you write it up below as an actual answer. – cartonn Jan 8 '13 at 22:11
• Don't be afraid to make other questions; this wasn't easy to find and we're discussing about how making the problem and its solution more visible on the site. – egreg Jan 8 '13 at 22:41