1. Use a 5V external power supply
Powering your BeagleBoard using USB OTG often causes booting fatal problem.
2. Prepare a serial cable
The BeagleBoard-xM provides a female DB9 port and requires a serial cable to connect the console to your host system. A DB9-to-USB cable does not work to me since I saw lots of junk data in the Hyper Terminal window or Tetra Term window in my Windows XP. The UART setting is:
Baud rate: 115200
Data: 8 bit
Stop: 1 bit
Flow control: None
3. Booting Angstrom Linux.
Boot Angstrom on the BeagleBoard-xM is with the microSD card that comes with the board, which contains an Angstrom image. Then you will see the Angstrom login console, then log in as root, no password. Then you are in root directory.
The following links provide more detail helpful information:http://www.ibm.com/developerworks/linux/library/l-beagleboard-xm/index.html