A sample latex document that can be used as a template for general latex usage.

document.tex

\documentclass[12pt]{article}
\usepackage{amsmath,amsfonts,amssymb,amsthm}
\usepackage[pdftex]{graphicx}

\setlength{\pdfpagewidth}{8.5in}
\setlength{\pdfpageheight}{11in}

\setlength{\topmargin}{0.0in}
\setlength{\voffset}{0.0in}
\setlength{\headheight}{0.0in}
\setlength{\headsep}{0.0in}
\setlength{\oddsidemargin}{0.0in}
\setlength{\hoffset}{0.0in}
\setlength{\textwidth}{6.5in}
\setlength{\textheight}{9in}
\setlength{\footskip}{0.0in}
\newtheorem*{thm}{Theorem}

\pagestyle{plain}
\title{Title Here}
\author{Daniel Haskin}
\begin{document}
\maketitle
\section{Hello}
\subsection{subsection}
\subsubsection{another}

Matrices:
\begin{equation*}
    \begin{matrix}
        a & b & c \\
        d & e & f
    \end{matrix}
\end{equation*}
Numbered equation:
\begin{equation}
    mind = blown
    \label{eq:mind}
\end{equation}
Align:
\begin{align*}
    \to x &= 4 \\
    e x &= \text{ciel}(\pi)
\end{align*}

\noindent no indent before paragraph.
Still on the paragraph.

After a line break

\begin{flushright}
    Righ-justified reference to equation with matrix~\ref{eq:mind} on page~\pageref{eq:mind}
\end{flushright}

Table with left, center, and right-aligned columns:
\begin{tabular}{ l | c || r }
    \hline
    1 & 2 & 3 \\
    4 & 5 & 6 \\
    7 & 8 & 9 \\
    \hline
\end{tabular}

And now a figure completely different:
\begin{figure}[h!]
    \begin{center}
        \includegraphics[width=0.25\textwidth]{file_name_without_ending}
    \end{center}
  \caption{a caption.}
  \label{fig:g}
\end{figure}
Figure~\ref{fig:g} is on page~\ref{fig:g}.

\end{document}