Are you running udev? Open a console window and enter 'ps -A | grep udevd'. If not, you can enter 'chmod 755 /etc/rc.d/rc.udev' then '/etc/rc.d/./rc.udev start'.
Plug in a USB device and see if it's detected. If it is, enter 'dmesg' in a console window and hit the 'End' key. You'll see all kinds of info about the USB device you've just plugged in. It should be referred to as sda1, meaning it's using the /dev/sda1 file. The next USB device you plug in should be /dev/sdb1, etc.
This probably isn't the way to do it, but I create directories under /mnt/ for each USB port- usb1, usb2, etc. I then add lines to /etc/fstab for each port as below:
Code:
/dev/sda1 /mnt/usb1 auto noauto,owner (or users, your choice),rw 0 0
I figure I'll never use more USB devices than I have ports. Using the above method I always know where every USB device is mounted.