Server side (Raspberry Pi running Raspbian)

Install tightvnc:

# apt-get install tightvncserver

Launch tightvnc with:

$ tightvncserver

It will ask you for a password and then show something like this:

New 'X' desktop is raspberrypi:1

Starting applications specified in /home/pi/.vnc/xstartup
Log file is /home/pi/.vnc/raspberrypi:1.log

Note the raspberrypi:1.

Client side (my laptop running Arch Linux)

Install tightvnc:

# pacman -S tightvnc

Connect to your Raspberry Pi with (adapt your ip address):

$ vncviewer 192.168.1.4:1