Step 1: Download and run Mr Engman's wireless config script (Network cable attached)
#Fetch @MrEngman config script
http://dl.dropbox.com/u/80256631/install-rtl8188cus.sh

#Make it executable
chmod u+x install-rtl8188cus.sh

#Run as root
sudo ./install-rtl8188cus.sh
Step 2: Configure /etc/network/interfaces to set up wlan0
...
auto wlan0
iface wlan0 inet dhcp
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
Step 3: Set up wpa_supplicant configuration (/etc/wpa_supplicant/wpa_supplicant.conf)
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
   ssid="YOUR_SSID"
   psk="YOUR WPA2 KEY"
   proto=RSN
   key_mgmt=WPA-PSK
   pairwise=TKIP
   auth_alg=OPEN
}
Step 4: Restart networking
/etc/init.d/networking restart