\input{preamble-standalone.ltx}
\begin{document}

% Ex. No. 250 (Section 31.4 : Own style)

\begin{tikzpicture}
    \tkzDefPoint(0,0){O}
    \tkzDefPoint(0,1){A}
    \tkzDrawPoints(O) % general style
    \tkzDrawPoints[mystyle,size=4](A) % my style
    \tkzLabelPoints(O,A)
\end{tikzpicture}

\end{document}