Make sure you initialise LCD properly. When the LCD has power applied to it, its memory contains garbage. When you use a write command to write something to the LCD, you maybe writing some of this garbage along with your intended transmission. Clear the LCD memory (the part you will write to and display) so that it is = 0. Then you can write on a clean screen. You may want to just clear the part of memory that would display one full screen on the LCD instead of clearing the entire LCD memory as this would save time for the microcontroller and reduce lag. this would mostly come into effect on a graphics LCD which has a big memory.
hope this helps