Wpa_supplicant

To configure wpa_supplicant with the standard Debian ifupdown system one has to add the
wireless interface to /etc/network/interfaces file in the folowing way:

allow-hotplug wlan0
iface wlan0 inet manual
        wpa-driver wext
        wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf

Next you can copy a decent template for the config file:

mkdir /etc/wpa_supplicant
copy /usr/share/doc/wpasupplicant/examples/wpa-roam.conf /etc/wpa_supplicant/wpa_supplicant.conf

And you need to add your network according to the examples in the file. More examples are in the
/usr/share/doc/wpasupplicant/examples folder.

After a new network is added to the wpa_supplicant.config file one needs to tell the daemon to refresh the list:

wpa_action wlan0 reload