Eliminate as many variables as possible.
This means.. throw out the serial monitor, make the microcontroller print to the LCD, and only that (I'd do this in the setup routine). Remove all other attached parts, use only the LCD.
Still garbage? have another LCD laying around? try swapping them. If the other is 'bugged' too, it is likely the wiring.
Have a multimeter? check each solderpoint.
If this yields no results, I'd suggest taking pictures of your hardware setup, and posting those together with your entire sketch.