Possible Duplicate:
How to create multilevel figure / table numbers?
Continuous v. per-chapter/section numbering of figures, tables, and other document elements
\documentclass{article}
\begin{document}
dude see Fig. \ref{myfig} !
\appendix{}
\section{my section heading}\label{sec:seclabel}
\begin{figure}[H]
\caption{mycaption}
\label{myfig}
\end{figure}
\end{document}
yields dude see Fig. 1 -- how do i make something that yields dude see Fig. A.1 (without manually doing Fig. \ref{sec:seclabel}.\ref{myfig}).