Arduino to breadboard with LM35 temp sensor
Check the baud rate of your serial monitor matches what you have set in your setup() function.  In the above code that is 9600.  If the baud rate is incorrect you typically get rubbish output in the serial monitor.



You may also want to change the Serial.print(tempC) to

Serial.println(tempC,2);


To get some decimal places.

As for the circuit ~




You don't need ARef connected. 
The LM35 VCC should be connected to Arduino 5V 
The LM35 GND to Arduino Gnd (any of them) 
Finally LM35 signal (Vout) to Arduino A0.