Download the image from http://www.raspberrypi.org/downloads. The latest version of Raspbian is called “wheezy”: 2012-12-16-wheezy-raspbian.zip. Unzip file and the result is “2012-12-16-wheezy-raspbian.img”.
Write it to SD card using the UNIX tool dd. Windows users should use Win32DiskImager.
When done, insert SD card into your Raspberry PI (don’t forget to shut down PI before this operation).
Boot the RPI!
Username: pi Password: raspberry