Configuring the rPi for remote X access (e.g. running X apps on the rPi and displaying them remotely on another linux machine): after installing ssh on the rPi, I set the IP to be static via /etc/network/interfaces 

auto lo

iface lo inet loopback
iface eth0 inet static
address 192.168.1.201
netmask 255.255.255.0
gateway 192.168.1.254

(note the non-standard gateway for me, thanks to BTHomeHub3)

and enabled X11 forwarding over ssh via /etc/ssh/ssh_config uncommenting

ForwardX11Trusted yes
AddressFamily any

then:
    ssh -X 1pi@192.168.1.201 

to log in remotely. Once in, you can enable X11 connections on the client machine (running X) with:
    xhost +

After this, typing X application names in your remote ssh shell on the rPi should cause them to display on your client linux box.

To enable networking with usb wifi instead, install and use wicd-curses to configure the wifi adapter.