Use this sketch to detect when your Arduino is tilted. Connect a tilt sensor to Analog pin 0 (A0)

tilt.ino

int out;

void setup()
{
	Serial.begin(9600); // sets the serial port to 9600
}

void loop()
{
	out = analogRead(0); // read analog input pin 0
	Serial.println(out, DEC);
	delay(100); // wait 100ms for next reading
}