This guide assumes you have a fair amount of knowledge of UNIX commands. You can learn more about the necessary commands and get more detail when you visit the official AudioPint wiki at http://www.audiopint.org.
Step 1: Setting up the OS: Format the USB Drive
Here's how to get the OS on the USB. For more detailed instructions, go to http://audiopint.org/download. Follow these instructions using the terminal in Linux.
Format the USB drive to the Ext2 filesystem. You can do this in Linux by running "gparted," the Gnome Partition tool. This creates space for the OS image.
Gparted will open up in a window that looks like the picture below. As shown, right-click on the USB drive (usually marked as sda1) and point to "Format to" and then click on "Ext2" (not ntfs, as shown in the image).
image found here: http://www.linuxgem.org/user_files/Image/gparted_7_big.jpg