The latest image can be downloaded from the Raspberry Pi download site – you have the choice between using a torrent client (recommended) or directly downloading a zip file if you don’t have a torrent client.
Strictly speaking, there is no preparation necessary, as the format information is contained in the image file. Any SD card of 2GB or greater capacity should be OK, however, it may be worth checking the known good cards list as there have been problems with some cards. Incidentally, it has been reported recently that many cards sold as Sandisk are counterfeit, so if in doubt, buy from a reputable supplier.
To be completed
Comprehensive instructions can be found here – there is little sense in recreating these directions here as they are not RISC OS specific.
Insert the SD card into the Raspberry Pi, and connect the other peripherals necessary. Power up the Pi, and you should see the RISC OS logo during the boot process, before being taken to the desktop. At first, there will be no IP connectivity as the default network setting is off. Please go to the Beginners FAQ:Network, Internet and Email to see how to set up networking for the first time. It is also likely that the screen resolution will need changing to suit your needs, so please see the Beginners FAQ:Look and Feel
If the initial boot (or subsequent boot) fails, the first likely candidate is the SD card. Check it is seated correctly, check that the contacts in the card slot aren’t damaged in any way, clean it all up, and try again. If this fails, it may be that the SD card has become corrupt, and needs re-imaging. This is a good time to remind all users of the importance of backups…