for command line users the best option is to use dd
Insert the USB drive and open terminal (Ctrl+Alt+T)
better be a root (sudo -i), don't be afraid believe in yourself
use "fdisk -l" to find the USB device
So in our case its /dev/sdb
Make sure the USB device is unmounted
`umount /dev/sdb1`
Assuming the .iso file is in your current working folder, type the below command and wait for it to finish.
`dd if=ubuntu-12.04.2-server-i386.iso of=/dev/sdb bs=4m`
MAC OS
diskutil unmount /dev/disk2
sudo dd if=manjaro-i3-18.0.4-stable-x86_64.iso of=/dev/disk2 bs=4m