I prefer #+SETUPFILE because the beauty is that that option is specific to loading a common org setup file.
* Latex Setup
** Change default font
Note that fontspec works with only xelatex (not pdflatex).
#+LaTeX_HEADER: \usepackage{fontspec}
#+LaTeX_HEADER: \setmainfont[Ligatures=TeX]{Linux Libertine O}
#+LaTeX_HEADER: \setmonofont[Scale=0.8]{Inconsolata-g}
** Sans serif fonts for section titles
#+LaTeX_HEADER: \usepackage{titlesec}
*** Formatting =section= titles
#+LaTeX_HEADER: \titleformat{\section}
#+LaTeX_HEADER: [hang] % titleformat shape
#+LaTeX_HEADER: {\usefont{T1}{qhv}{b}{n}\selectfont\Large} % titleformat format "qhv" - TeX Gyre Heros, "b" - bold
#+LaTeX_HEADER: {\thesection} % titleformat label
#+LaTeX_HEADER: {0.6em} % titleformat separation
#+LaTeX_HEADER: {} % code preceeding title body
*** Formatting =subsection= titles
#+LaTeX_HEADER: \titleformat{\subsection}
#+LaTeX_HEADER: [hang] % titleformat shape
#+LaTeX_HEADER: {\bfseries\large} % titleformat format
#+LaTeX_HEADER: {\thesubsection} % titleformat label
#+LaTeX_HEADER: {0.4em} % titleformat separation
#+LaTeX_HEADER: {} % code preceeding title body
*** TODO Look into using the =sectsty= package instead of =titlesec= because of its compatibility issues with =hyperref=
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The awesome thing is that org will load only the "setup" stuff from a SETUPFILE file.. so it will pick up the #+LaTeX_HEADER lines from above, but not "
* Latex Setup" or "** Change default font" or other things.