The easiest way to use libnfc with the Adafruit NFC Breakout is via UART, since it's well-supported by libnfc out of the box. Unfortunately the UART port on the Pi is already dedicated to other purposes, and needs to be freed up for libnfc.
The following steps (based on a clean Raspbian install via noobs) should free UART up for us:
From the main menu, select option 7 (Serial), then select 'No' to disable shell and kernel messages via UART.
On the latest Jessie Raspbian, you may also need to enable the UART for user usage! Edit config.txt with
sudo nano /boot/config.txt
and remove the line
if it exists. And add at the end of the file
Save the file
From the command prompt enter the following commands to reboot your Raspberry Pi board, freeing UART up in the process: