No network manager in XFCE

I had this problem on Debian Lenny (Testing), in XFCE, though I'm sure it applies to more distributions.

If you can't see your wireless networking icon on your panel, you may need to start Network Manager.
Go to Settings -> Settings Manager -> Autostarted apps and add the command "nm-applet --sm-disable".

You may also need to add a "system tray" by right-clicking on the panel and going to "add new item".

Then search for and add "system tray". This is where the Network Manager icon should appear