The easiest way i've found to play with USB is to get iso of os or utility you want to play with. Use gparted to create partition table on usb then to add primary partition of fat32, I normally then manage flags click on boot . Then use
http://unetbootin.github.io/ which has a GUI that lets you select ios you want & where you want to put it.
#fdisk -l with usb in slot will show the usb eg /dev/sdb /dev/sdc
Obviously make sure you don't pick something like /dev/sda that will be your PC hard-drive !
using unetbootin i've got
http://www.hirensbootcd.org on usb
