header.tex

\documentclass[a4paper]{article}

% variables! for nice stuff.
\newcommand{\documentTitle}{TITLE OF YOUR DOCUMENT}
\newcommand{\documentAuthor}{YOUR NAME}
\newcommand{\documentDate}{\today}

% unicode please
\usepackage[utf8]{inputenc}

% ams Maths packages
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{amsfonts}

% fixes font sizing
\usepackage{fix-cm}

% theorem stuff
\newtheorem{defn}{Definition}[section]
\newtheorem{thm}{Theorem}[section]
\newtheorem{prop}{Proposition}[section]
\newtheorem{exmp}{Example}[section]
\newtheorem{remark}{Remark}[section]

% formatting page
\usepackage[a4paper]{geometry}

% fancy header
\usepackage{fancyhdr}
\fancypagestyle{plain}{%
  \fancyhf{}
  \fancyhead[L]{\rule[-2ex]{0pt}{2ex}\small \leftmark}
  \fancyhead[R]{\small \rightmark}

  \fancyfoot[L]{\small \documentAuthor}
  \fancyfoot[C]{-- \thepage\ --}
  \fancyfoot[R]{\small \documentDate} 

  \renewcommand{\headrulewidth}{0.4pt}
  \renewcommand{\footrulewidth}{0.4pt}}
\pagestyle{plain}

% fix a warning
\setlength{\headheight}{17pt}

% a nice font
\usepackage[light,math]{iwona}
\usepackage[T1]{fontenc}

% colour package is useful
\usepackage[dvipsnames]{xcolor}

% images
\usepackage{graphicx}
\graphicspath{{./img/}}
\usepackage{float}
\usepackage{wrapfig}

% nice code, and make it pretty
\usepackage{listings}
\lstset{
    basicstyle=\footnotesize\ttfamily,
    numbers=left,
    numberstyle=\tiny,
    identifierstyle=\color{CornflowerBlue},
    keywordstyle=\color{RoyalBlue},
    stringstyle=\color{ForestGreen},
    commentstyle=\color{BrickRed},
    showspaces=false,
    showtabs=false,
    frame=single
}

% margin note
\newcommand{\marginnote}[1]{\marginpar{\footnotesize\textcolor{red}{#1}}}
\newcommand{\note}[1]{\begin{center}\textcolor{red}{#1}\end{center}}

% let the fun begin!
\begin{document}

% title
\title{\documentTitle}
\author{\documentAuthor}
\date{\documentDate}
\maketitle
\newpage

% table of contents
\tableofcontents
\newpage

% start here!

\end{document}