Andrea:
I see a few problems:
(1) You are using digital pins 0 and 1 for your LCD but they are also used by the serial monitor. You cannot change the serial monitor so you will have to use different pins for your LCD.
(2) There is no lcd.println() function. You won't blow up your Arduino, but you will get some funny characters on your display.
(3) lcd.clear() should work but it takes a relatively long time to complete so it is not a good idea to use it in loop().
Don