>I'm writing a latex documents, and it's boring to build a table word
>by word. Is there any useful shortcuts in emacs for latex that allows
>to build tables, to include images quickly? For example, having a key
>sequence to build an table automatically in emacs

I write a lot latex with emacs (using latex mode).  The key sequence
that I find most helpful is C-c C-e (aka latex-close-block).  C-c C-e
finds the most recent \begin{FOO} and inserts the matching \end{FOO}.

I don't know of any dedicated latex-mode commands for building tables
or stubbing out figure environments.  But I can suggest two
alternatives.

The first alternative is abbrev mode.  You could (say) define an
abbrev that inserts

   \begin{figure}
   \begin{center}
   \includegraphics{}
   \end{center}
   \caption{}\label{}
   \end{figure}

whenever you type "ltxfigure".

For more on abbrevs, see

   M-x info RET
   M-x Info-goto-note RET (Emacs)Abbrevs RET

Alternative two: for tables, I sometimes find that it's easier to
write the table using org-mode, have org-mode convert the table to
latex, and then insert the generated table back into the .tex file.

   M-x org-info

And look for sections on "Tables" and "export".

Steve