As you know, the Arch Linux developers update their distribution monthly. Yesterday, the Arch Linux 2013.06.01 was released.
To update to the latest Arch Linux, if you have it installed, just open a terminal and run:
$ sudo pacman -Syu
If you don’t have Arch Linux installed, but want to test it, you can download Arch Linux 2013.06.01 from here, or by torrent, from here.
To keep your system up to date, just type sudo pacman -Syu from time to time, or schedule a system cron job to update Arch Linux (this will run the command weekly, by root):
$ sudo sh -c 'echo "@weekly root pacman -Syu" >> /etc/crontab'