\documentclass[11pt,a4paper]{article}  % or report, book, beamer
\usepackage[margin=1in]{geometry}
\usepackage{amsmath,amssymb,amsfonts}
\usepackage{graphicx,booktabs}
\usepackage{xcolor}
\usepackage[colorlinks=true,linkcolor=blue,citecolor=blue,urlcolor=blue]{hyperref}
% \usepackage[backend=biber,style=numeric]{biblatex}
% \addbibresource{refs.bib}

\title{Title}
\author{Your Name}
\date{\today}

\begin{document}
\maketitle
\begin{abstract} ... \end{abstract}
\tableofcontents
\section{Introduction}
...
% \bibliographystyle{plain}\bibliography{refs}   % BibTeX
% \printbibliography                             % biblatex
\end{document}

\usepackage[margin=1in]{geometry}
\usepackage{setspace}\onehalfspacing
\usepackage{fancyhdr}
\pagestyle{fancy}
\usepackage{siunitx}          % units and numbers
\usepackage{cleveref}         % after hyperref
\DeclareMathOperator*{\argmax}{arg\,max}
\newcommand{\vect}[1]{\boldsymbol{#1}}

\begin{itemize}
  \item Bullet
\end{itemize}

\begin{enumerate}
  \item Numbered
\end{enumerate}

\begin{description}
  \item[Term] Definition
\end{description}

\part{...}            % book
\chapter{...}         % report/book
\section{...}
\subsection{...}
\subsubsection{...}
\paragraph{...}
\section*{Unnumbered}
\addcontentsline{toc}{section}{Unnumbered}

\section{Methods}\label{sec:methods}
\begin{equation}\label{eq:main} E=mc^2 \end{equation}
\begin{figure}
  ...
  \caption{Pipeline}\label{fig:pipe}
\end{figure}

See Section~\ref{sec:methods}, Eq.~\eqref{eq:main}, Figure~\ref{fig:pipe}.
% with cleveref:
% \cref{fig:pipe}  \Cref{sec:methods}

\usepackage{hyperref}
\url{https://oleafly.com}
\href{https://oleafly.com}{Oleafly}
\hypersetup{pdftitle={My Paper}, pdfauthor={You}}

\begin{align}
  a &= b + c \label{eq:a} \\
  d &= e + f \notag
\end{align}

\frac{a}{b} \dfrac{a}{b} \tfrac{a}{b}
\sqrt{x} \sqrt[n]{x}
x_i  x^{2n}  x_{ij}^{2}
f'  f''  \dot{x} \ddot{x}

\alpha \beta \gamma \delta \epsilon \varepsilon \zeta \eta
\theta \vartheta \iota \kappa \lambda \mu \nu \xi
\pi \varpi \rho \varrho \sigma \varsigma \tau \upsilon
\phi \varphi \chi \psi \omega
\Gamma \Delta \Theta \Lambda \Xi \Pi \Sigma \Upsilon \Phi \Psi \Omega

\pm \mp \cdot \times \div \ast \star \circ \bullet
\leq \geq \neq \approx \equiv \sim \simeq \propto \ll \gg
\in \notin \subset \subseteq \supset \supseteq \cup \cap \emptyset
\to \mapsto \Rightarrow \Leftrightarrow \uparrow \downarrow
\infty \partial \nabla \ell \forall \exists \neg \land \lor

\hat{x} \bar{x} \tilde{x} \vec{x} \dot{x} \ddot{x}
\widehat{xyz} \overline{ABC}
\mathbb{N Z Q R C}   \mathcal{L}   \mathfrak{g}
\mathrm{d}x   \mathbf{A}   \boldsymbol{\beta}

\sum_{i=1}^n \prod_{i=1}^n \int_a^b \oint \iint
\lim_{x \to 0} \max_x \min_x \inf \sup
\frac{dy}{dx} \frac{\partial f}{\partial x}
\argmax_x   % after \DeclareMathOperator*{\argmax}{arg\,max}

\begin{pmatrix} a & b \\ c & d \end{pmatrix}  % ( )
\begin{bmatrix} a & b \\ c & d \end{bmatrix}  % [ ]
\begin{vmatrix} a & b \\ c & d \end{vmatrix}  % | |
\begin{array}{r|cc} 1 & 2 & 3 \\ \hline 4 & 5 & 6 \end{array}

f(x) =
\begin{cases}
  x^2 & x \ge 0 \\
  -x  & x < 0
\end{cases}

\left( \frac{a}{b} \right)
\left\{ x : x > 0 \right\}
\langle v, w \rangle
\lvert x \rvert \lVert v \rVert

\usepackage{booktabs}
\begin{table}[htbp]
  \centering
  \caption{Results}\label{tab:res}
  \begin{tabular}{lcc}
    \toprule
    Model & Acc & F1 \\
    \midrule
    Baseline & 0.81 & 0.79 \\
    Ours & 0.87 & 0.86 \\
    \bottomrule
  \end{tabular}
\end{table}

\usepackage{graphicx}
\begin{figure}[htbp]
  \centering
  \includegraphics[width=0.8\textwidth]{figures/plot.pdf}
  \caption{Overview.}\label{fig:plot}
\end{figure}

See \cite{knuth84} and \cite{a,b}.
\bibliographystyle{plain}  % abbrv, alpha, ieeetr, apalike, ...
\bibliography{refs}

\usepackage[backend=biber,style=numeric]{biblatex}
\addbibresource{refs.bib}
...
\cite{knuth84} \parencite{knuth84} \textcite{knuth84}
\printbibliography

\usepackage{natbib}
\citet{key}   % Author (year)
\citep{key}   % (Author, year)
\citep*{key}  % Author, year

@article{knuth84,
  author  = {Knuth, Donald E.},
  title   = {Literate Programming},
  journal = {The Computer Journal},
  year    = {1984},
  volume  = {27},
  pages   = {97--111}
}

\usepackage[a4paper,margin=1in]{geometry}
\usepackage{setspace}\onehalfspacing
\setlength{\parindent}{0pt}
\setlength{\parskip}{0.6em}

% Xe/Lua
\usepackage{fontspec}
\setmainfont{Times New Roman}

\usepackage{xcolor}
\textcolor{red}{warn}
\textcolor[HTML]{2563EB}{brand}
\definecolor{brand}{HTML}{2563EB}
\colorbox{gray!12}{highlight}

\usepackage{tikz}
\usetikzlibrary{positioning,arrows.meta}
\begin{tikzpicture}[node distance=1.4cm]
  \node[draw,rounded corners] (a) {In};
  \node[draw,rounded corners,right=of a] (b) {Out};
  \draw[-Latex] (a) -- (b);
\end{tikzpicture}

\documentclass{beamer}
\usetheme{Madrid}
\title{Talk}\author{You}
\begin{document}
\frame{\titlepage}
\begin{frame}{Results}
  \begin{itemize}
    \item<1-> First
    \item<2-> Second
  \end{itemize}
  \pause
\end{frame}
\end{document}

\usepackage{amsthm}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{lemma}[theorem]{Lemma}
\begin{theorem}[Name]
  Statement.
\end{theorem}
\begin{proof}
  ...
\end{proof}

% Chemistry
\usepackage[version=4]{mhchem}
\ce{H2O} \ce{CO2 + C -> 2CO}

% Physics
\usepackage{braket}
\braket{\psi|\phi} \braket{\psi|A|\phi}

% Code
\usepackage{listings}
\begin{lstlisting}[language=Python]
def f(x):
    return x**2
\end{lstlisting}