I'm a starter of Raspberry Pi and I found that Raspberry Pi doesn’t have the usb port that could directly connect to the pc, so that I pick a Seeeduino as an Uart to Usb converter to putty up my Pi. :p
Step by Step Introduction
Connect the wires.
Write a simple code into arduino.
Open the Putty to view the terminal of your Pi. Remember the set the right arduino port and speed.