The first level of division within chapters is the
section. The two forms are similar to the two forms
of the \chapter command:
\section{SECTION TITLE}
\section[SHORT TITLE]{SECTION TITLE}
If you use the first form, the SECTION TITLE will appear in the table of contents. With the second form, the SECTION TITLE appears at the beginning of the section, but the SHORT TITLE appears in the table of contents.
You may subdivide sections two levels further with \subsection and \subsubsection
commands. These commands have the same optional and
required arguments.
The way you capitalize section, subsection, and subsection titles is arbitary, but be consistent throughout the thesis.
Examples:
\section{MAGNETOHYDRODYNAMICS OF METEOR BREAKUP}
\section{Magnetohydrodynamics of Meteor Breakup}
\section{Magnetohydrodynamics of meteor breakup}
\subsection[Ethical Considerations]{Ethical Considerations of
Experimentation With Live Rocks}