1) set router name and password
2) connect
(3) sometimes "dhclient wlan0" necessary)

The easiest way to set your router SSID and password is to add an entry to /etc/wpa_supplicant.conf that should be something like this:

network={
    ssid="ssid_name"
    psk="password"
}

Or, to increase security, use the wpa_passphrase command to use a hashed password in the conf file (so type wpa_passphrase yourssid yourpassword)

Then:

sudo wpa_supplicant -B -iwlan0 -c/etc/wpa_supplicant.conf -Dwext
sudo dhclient wlan0

The seemingly lacking space between -i and wlan0 or between -c and /etc is not a typo, it has to be that way.
Depending on your wireless card, you might need to replace the wext part with another driver, such as nl80211.

Absolutely minimal (533 Mb 32 bit, in German).

I did only use wireless at installations time.

The installation installs a lot of stuff I never will use on a server (dictionaries and spells, more than only one) but I don't find some spontan usuable way to restart internet (it was IN at installation's time!)...

How to restart wireless internet to continue installation?