It is not really necessary to use REVTeX4, but is is strongly recommended and will make preparing your manuscript easier. Download it (for free).

If your document begins with \documentstyle, you are using LaTeX 2.09. Please do not use this older version. Instead, use \documentclass which is used by LaTeX2e, which also is freely available.

\documentclass[12pt,aps,prb,preprint]{revtex4}   % style for Physical Review B and AJP are similar

\usepackage{amsmath}    % need for subequations
%\usepackage{amsfonts}  note how statements can be commented out
%\usepackage{amssymb}
\usepackage{graphicx}   % for figures

\newcommand{\ajp}{AJP}  % example of a definition of a macro
\begin{document}

\title{Preparation of manuscripts for the American Journal of Physics\\
using \LaTeX}
%Lines break automatically or can be forced with \\
\author{Harvey Gould}
 \altaffiliation[Also at ]{home.}  %  optional
 \affiliation{Clark University, Department of Physics, Worcester,
MA 01610}
 \email{hgould@clarku.edu}   %optional
\author{Jan Tobochnik}
\affiliation{Kalamazoo College, Department of Physics, Kalamazoo,
MI 49007}
\date{\today}

\begin{abstract}
We gave some examples of the use of \LaTeX\ that we hope will be
helpful in preparing manuscripts for \ajp.
\end{abstract}

\maketitle

\section{Introduction}
\TeX\ looks more difficult than it is. It is
almost as easy as $\pi$. See how easy it is to make special
symbols such as $\alpha$,
$\beta$, $\gamma$,
$\delta$, $\sin x$, $\hbar$, $\lambda$, $\ldots$ We also can make
subscripts
$A_{x}$, $A_{xy}$ and superscripts, $e^x$, $e^{x^2}$, and
$e^{a^b}$. We will use \LaTeX, which is based on \TeX\ and has
many higher-level commands (macros) for formatting, making
tables, etc. More information can be found in
Ref.~\onlinecite{latex}, a book written by Kopka and
Daly.\cite{latex}

We just made a new paragraph. Extra lines and spaces make no
difference. Note that all formulae are enclosed by
\$ and occur in \textit{math mode}.

The default font is Computer Modern. It includes \textit{italics}
or {\it italics}, \textbf{boldface} or {\bf boldface},
\textsl{slanted} or {\sl slanted}, and \texttt{monospaced} or {\tt
monospaced} (typewriter) fonts.

\section{Equations}
Let us see how easy it is to write equations.
\begin{equation}
\Delta =\sum_{i=1}^N w_i (x_i - \bar{x})^2 .
\end{equation}
It is usually a good idea to number equations, but we can have a
equation without a number by writing
\begin{equation*}
P(x) = \frac{x - a}{b - a} , 
\end{equation*}
or
\begin{equation}
g = \frac{1}{2} \sqrt{2\pi} . \nonumber
\end{equation}

We can give an equation a label so that we can refer to it later.
\begin{equation}
\label{eq:ising}
E = -J \sum_{i=1}^N s_i s_{i+1} ,
\end{equation}
Equation~(\ref{eq:ising}) expresses the energy of a configuration
of spins.\cite{footnotes} If we use the amsmath package, we could write Eq.~\eqref{eq:ising}.

We can define our own macros to save typing. For example, suppose
that we introduce the macros:
\begin{verbatim}
 \newcommand{\lb}{{\langle}}
 \newcommand{\rb}{{\rangle}}
\end{verbatim}
\newcommand{\lb}{{\langle}}
\newcommand{\rb}{{\rangle}}
% verbatim useful for program listings
Then we can write the average value of $x$ as
\begin{verbatim}
\begin{equation}
\lb x \rb = 3
\end{equation}
\end{verbatim}
The result is
\begin{equation}
\lb x \rb = 3 .
\end{equation}

Examples of more complicated equations:
\begin{equation}
I = \! \int_{-\infty}^\infty f(x)\,dx \label{eq:fine}.
\end{equation}
We can do some fine tuning by adding small amounts of horizontal
spacing:
\begin{verbatim}
 \, small space       \! negative space
\end{verbatim}
as is done in Eq.~(\ref{eq:fine}).

We also can align several equations:
\begin{eqnarray}
a & =& b \\
c &=& d ,
\end{eqnarray}
or number them as subequations:
\begin{subequations}     % need amsmath package
\begin{eqnarray}
a & =& b \\
c &=& d .
\end{eqnarray}
\end{subequations}
How would you suppress the equation numbers in these two examples?
A slightly better way to align equations use the amsmath package:
\begin{subequations} 
\begin{align}
a & = b \\
c &= d .
\end{align}
\end{subequations}
Can you notice the difference?
Some other examples:
\begin{equation}
\label{eq:mdiv}
m(T) =
\begin{cases}
0 & \text{$T > T_c$} \\
\bigl(1 - [\sinh 2 \beta J]^{-4} \bigr)^{\! 1/8} & \text{$T < T_c$}
\end{cases}
\end{equation}
\begin{align}
\textbf{T} &=
\begin{pmatrix}
T_{++} \hfill & T_{+-} \\
T_{-+} & T_{--} \hfill 
\end{pmatrix} \nonumber \\
& =
\begin{pmatrix}
e^{\beta (J + B)} \hfill & e^{-\beta J} \hfill \\
e^{-\beta J} \hfill & e^{\beta (J - B)} \hfill
\end{pmatrix}
\end{align}
\newcommand{\rv}{\textbf{r}}
\begin{equation}
\sum_i \vec A \cdot \vec B = -P \! \int \! \rv \cdot
\hat{\mathbf{n}}\, dA = P \! \int \! {\vec \nabla} \cdot \rv\, dV.
\end{equation}

\section{Lists}

Some example of formatted lists include the
following:

\begin{enumerate}

\item bread

\item cheese

\end{enumerate}

\begin{itemize}

\item Tom

\item Dick

\end{itemize}

An example of a table is given in Table~\ref{tab:tc} at the end
of the manuscript and examples of how to include figures are
shown in Figs.~\ref{fig:sine} and \ref{fig:lj}.

\section{Special Symbols}

\subsection{Common Greek letters}

These commands may be used only in math mode. Only the most common
letters are included.

$\alpha, 
\beta, \gamma, \Gamma,
\delta,\Delta,
\epsilon, \zeta, \eta, \theta, \Theta, \kappa,
\lambda, \Lambda, \mu, \nu,
\xi, \Xi,
\pi, \Pi,
\rho,
\sigma, 
\tau,
\phi, \Phi,
\chi,
\psi, \Psi,
\omega, \Omega$

\subsection{Special symbols}

The derivative is defined as
\begin{equation}
{dy \over dx} = \lim_{\Delta x \to 0}{\Delta y
\over
\Delta x}
\end{equation}
\begin{equation}
f(x) \to y \quad {\rm as} \quad x \to
x_{0}
\end{equation}
\begin{equation}
f(x) \mathop {\longrightarrow}
\limits_{x \to x_0} y
\end{equation}

\noindent Order of magnitude:
\begin{equation}
\log_{10}f \simeq n
\end{equation}
\begin{equation}
f(x)\sim 10^{n}
\end{equation}
Approximate equality:
\begin{equation}
f(x)\simeq g(x)
\end{equation}
\TeX\ is simple if we keep everything in proportion:
\begin{equation}
f(x) \propto x^3 .
\end{equation}

We can skip some space by using a command such as
\begin{verbatim}
\bigskip    \medskip    \smallskip    \vspace{1pc}
\end{verbatim}
The space can be negative.

And it sometimes is convenient to write $\tilde x$,
$\widetilde{xy}$, $\overline{A}$, \%, accents: Schr\"odinger
and \'e (or any other letter \'z).

\section{Literal text}
It is desirable to print program code exactly as it is typed in a
monospaced font. Use \verb=\begin{verbatim}= and
\verb=\end{verbatim}= as in the following example:
% = sign used as a delimiter
\begin{verbatim}
  public void computeArea()
  {
    this.area = this.length*this.length;
    System.out.println("Area = " + this.area);
   }
\end{verbatim}
The command \verb=\verbatiminput{programs/Square.java}= allows
the file \texttt{Square.java} in the direction \texttt{programs}
to be listed without changes.

\appendix
\section{Some dos and don'ts}

\begin{enumerate}

\item Note the \ajp\ style for books\cite{latex} and
articles.\cite{1d}

\item Also note the American convention of the positions
of citations.

\item Do not skip a line before \verb=\begin{equation}= or after 
\verb=\end{equation}=.
\end{enumerate}

\begin{acknowledgments}
Be sure to thank your colleagues and any granting agencies.
\end{acknowledgments}

\begin{thebibliography}{5}

\bibitem{latex}Helmut Kopka and Patrick W. Daly, \textsl{A Guide to
\LaTeX: Document Preparation for Beginners and Advanced Users} (Addison-Wesley, Reading, MA, 1999), 3rd. ed. 

\bibitem{footnotes}It is necessary to process a file twice to
get the counters correct. \ajp\ does not use footnotes.

\bibitem{1d}B. C. Freasier, C. E. Woodward, and R. J. Bearman,
``Heat capacity extrema on isotherms in one-dimension: Two
particles interacting with the truncated Lennard-Jones potential
in the canonical ensemble,'' J. Chem. Phys. {\bf 105}, 3686--3690
(1996).


\end{thebibliography}

\newpage
\section*{Tables}

Tables are a little difficult until you get the
knack.
\LaTeX\ automatically calculates the width of the columns. Tables
should be placed at the end of the manuscript.

\begin{table}[h]
\begin{center}
\begin{tabular}{|l|l|r|l|}
\hline
lattice & $d$ & $q$ & $T_{\rm mf}/T_c$ \\
\hline
square & 2 & 4 & 1.763 \\
\hline
triangular & 2 & 6 & 1.648 \\
\hline
diamond & 3 & 4 & 1.479 \\
\hline
simple cubic & 3 & 6 & 1.330 \\
\hline
bcc & 3 & 8 & 1.260 \\
\hline
fcc & 3 & 12 & 1.225 \\
\hline
\end{tabular}
\caption{\label{tab:tc}Comparison of the mean-field predictions
for the critical temperature of the Ising model with exact results
and the best known estimates for different spatial dimensions $d$
and lattice symmetries.}
\end{center}
\end{table}

\newpage
\section*{Figures}
It is easy to include encapsulated postscript files (see Figure~\ref{fig:sine}). We can make figures bigger or smaller by scaling them. Figure~\ref{fig:lj} has been scaled by 80\%.
Figures should be placed at the end of the manuscript and sent as separate files. It also is possible to include pdf files.

\begin{figure}[h]
\begin{center}
\includegraphics{figures/sine.eps}
\caption{\label{fig:sine}Show me a sine.}
\end{center}
\end{figure}

\begin{figure}[h]
\begin{center}
\scalebox{0.80}{\includegraphics{figures/lj.eps}}
\caption{\label{fig:lj}Plot of the
Lennard-Jones potential
$u(r)$. The potential is characterized by a length
$\sigma$ and an energy
$\epsilon$. This potential is applied in Ref.~\onlinecite{1d}.}
\end{center}
\end{figure}

\end{document}