Plotting more than one series on the same graph

I'm new to R and have searched for help and consulted the the pdf
manuals, but I can't seem to figure out how to plot more than one
series on the same graph.

I've tried using multiple par(new=TRUE) statements such as

plot(series1, ci.type="line", col="red", lwd=2, ci.lty=0, ci.col="red")
par(new=TRUE)
plot(series2, ci.type="line", col="green", lwd=2, ci.lty=0, ci.col="green")
par(new=TRUE)
plot(series3, ci.type="line", col="blue", lwd=2, ci.lty=0, ci.col="blue")

and this does plot the three series on one graph, but makes a mess of
the y-axis.

There must be a more elegant solution.

Also, I wonder why the final series (series 3) doesn't plot until I
manually hit <enter>?

Thanks for any help, Mark