(handy for running things like Arduino IDE as a regular user)
1) Create the udev rules file:
as root:
vi /etc/udev/rules.d/50-usb.rules and add one of the following
Allow access by everyone (kinda un-safe)
KERNEL=="ttyUSB[0-9]*",MODE="0666" KERNEL=="ttyACM[0-9]*",MODE="0666"
Allow access by members of the 'wheel' group-
KERNEL=="ttyUSB[0-9]*",GROUP="wheel",MODE="0660" KERNEL=="ttyACM[0-9]*",GROUP="wheel",MODE="0660"