给表格加注释的确是很多TeX用户不好用的地方，这里提供一个样式和代码，或许对于你的学习使用有所帮助，样式如下：

代码如下：

\documentclass[11pt,a4paper,english]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage[font=small,labelfont=bf,tableposition=top]{caption}
\usepackage{booktabs}
\usepackage{threeparttable}

\begin{document}
  \begin{table}[!ht]
    \caption{A table with notes}\label{tab:tablenotes}
    \centering
    \begin{threeparttable}
      \begin{tabular}{*4{c}}\toprule
        Table head\tnote{1} & Table head\tnote{1} & Table head\tnote{2} & Table head\tnote{2} \\ \midrule
        Some values & Some values & Some values & Some values \\
        Some values & Some values & Some values & Some values \\
        Some values & Some values & Some values & Some values \\
        Some values & Some values & Some values & Some values \\ \bottomrule
      \end{tabular}
      \begin{tablenotes}
        \footnotesize
        \item[1] The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog.
        \item[2] The quick brown fox jumps over the lazy dog.
      \end{tablenotes}
    \end{threeparttable}
  \end{table}

转自http://blog.sina.com.cn/s/blog_5e16f1770102dxpi.html

备注：

如果只有一项可以：\item[] The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog.