Have a look at
- the clsguide about macros for package/class writers, and how to setup own classes
- the dtxtut about how to pack your file as most package/class authors do
- the LaTeX Companion about writing own classes
Since you are a beginner it is maybe preferable to start with an easy \input file and not writing a class. Just create a file (e.g.) header.tex
\documentclass{article}
\usepackage[margin=2cm]{geometry}
% ...
and us it like
\input{header}
\begin{document}
Hello World!
\end{document}
To make you file available for multiple project you can save it in the user texmf tree. To find the right path call kpsewhich -var-value=TEXMFHOME in your terminal. It is possible that you must create the path first. then store your header.tex at <TEXMFHOME>/tex/latex/header.tex
geometrypackage. For fonts, you usually include a package specifically for a font you want to use. – yo' Apr 02 '12 at 12:46