I use them to check whenever a user press a push button.
I defined them in this way
#define Power A0
#define Select A1
#define Up A2
#define Down A3
#define Left A4
#define Right A5
and in setup()
//Setup the Joystick buttons as inputs
pinMode(Power, INPUT);
pinMode(Up, INPUT);
pinMode(Down, INPUT);
pinMode(Left, INPUT);
pinMode(Right, INPUT);
pinMode(Select, INPUT);
//Enable pullups on Joystick buttons
digitalWrite(Power, HIGH);
digitalWrite(Up, HIGH);
digitalWrite(Down, HIGH);
digitalWrite(Left, HIGH);
digitalWrite(Right, HIGH);
digitalWrite(Select, HIGH);
and using 6 push buttons between GND and each analog input.
My project is a MP3 player