You need a SD card, 2GB minimum preferably 4GB and as fast as you can get (speeds up writing). Get a couple.

Download the operating system file from raspberry-pi.org Start with Raspbian “wheezy”. It’s easy enough to change later on.

Unzip the download and you get a image file (.img) that has to be loaded onto the SD card. Not simply copied over.

I use Linux and this worked for me (change the img file location and SD card designation to suit):

sudo dd bs=4M if=/home/paul/Downloads/apps/raspberry_pi/2012-09-18-wheezy-raspbian.img of=/dev/sdd

This will take a few minutes or a long time if you have a slow SD card.

Put the SD card in the R-Pi, connect a TV, keyboard and mouse.

Power up the R-Pi using a 700mA or greater phone charger or similar 5V DC power supply.
You should see the boot up on the TV leading to a setup menu that only appears on first time boot.

Add a new User

To add a new user

sudo adduser paul

To make the new user a super-user:

adduser paul sudo