How can I “reset” an Arduino board?

Question

I\'ve uploaded a sketch to an Arduino Uno whose loop is something like this:

void loop(){
    Serial.println(\"Hello, World!\");
}

So, now,

Answer 1

Arduino Leonardo board:

1. Unplug the USB cable
2. Connect the RX Pin to ground
3. Plug in the USB cable
4. Upload a new program
5. Remove the USB cable
6. Remove the RX grounding