ArchLinux is a great operating system for low-cost ARM based embedded devices, such as the Raspberry Pi and BeagleBone Black. The development team for the ARM port is doing an excellent job optimizing and updating the package repository.
The official website has instructions for installing ArchLinux ARM on the BBB, but is missing the details for post-installation steps that are generally not known by users who are just starting with ArchLinux. The best, most detailed and up-to-date ArchLinux installation tutorial I found is the one written by The Mukt, but at the time of this writing it appears to be offline.
Below you can find the condensed summary of the installation steps that I usually take on BeagleBones.