Debian wireless networking configs (at /etc/network/interfaces)

DHCP wireless configuration

# DHCP network config 

## Set your interface, e.g. wlan0
allow-hotplug <INTERFACE>
## Set your network SSID and password
iface <INTERFACE> inet dhcp
        wpa-ssid <SSID>
        wpa-psk <PASSWORD>

STATIC wireless configuration

# STATIC IP network config 

## Set your interface, e.g. wlan0
allow-hotplug <INTERFACE>
## Set your network SSID and password together with the desired IP and router config
iface <INTERFACE> inet static
        wpa-ssid <SSID>
        wpa-psk <PASSWORD>
        address <IP>          # 192.168.1.150
        netmask <NETMASK>     # 255.255.255.0
        gateway <GATEWAY>     # 192.168.1.254
        

After add one of them, relaunch the network interface using:

sudo ifdown <INTERFACE>
sudo ifup <INTERFACE>

And check it:

ifconfig