I'm not running debian, but I set up my network with the /etc/network/interfaces
file. Whatever is available comes up at boot.
iface lo inet loopback
iface eth0 inet static
# These settings are for a 192.168.0.1 network
# broadcast 192.168.0.255
# address 192.168.0.8
# netmask 255.255.255.0
# gateway 192.168.0.1
iface wlan0 inet static
makes it come up at boot.
If you want dhcp, not static (remember to update /etc/resolv.conf
if you are using static IP) Then just use
iface wlan0 inet dhcp
instead of static and no need for broadcast, netmask, gateway etc entries.
See man interfaces