Configuring WiFi on a Raspberry Pi Running Raspbian (Debian)

interfaces

# Open the networking configuration file using your favorite editor (vi, nano, etc....)

sudo vi /etc/network/interfaces

# Enter the following:

auto lo

iface lo inet loopback
iface eth0 inet dhcp

allow-hotplug wlan0
auto wlan0

iface wlan0 inet dhcp
  wpa-ssid "MYSSID"
  wpa-psk "MYSSIDPASSWORD"
  
# EOF #############################

# NOTE: If your network's SSID is set to hidden, then enter the following, instead of the syntax above:

auto lo

iface lo inet loopback
iface eth0 inet dhcp

auto wlan0
allow-hotplug wlan0
iface wlan0 inet dhcp
   wpa-scan-ssid 1
   wpa-ap-scan 1
   wpa-key-mgmt WPA-PSK
   wpa-proto RSN WPA
   wpa-pairwise CCMP TKIP
   wpa-group CCMP TKIP
   wpa-ssid "MYSECRETSSID"
   wpa-psk "MYSSIDPASSWORD"

iface default inet dhcp

# EOF #############################

# Restart the network interface to apply changes without a reboot:

sudo /etc/init.d/networking stop
sudo /etc/init.d/networking start