If you apply power to the LCD, with the contrast pin grounded, the display usually shows a single line of block characters. That means it is powered correctly and is basically functional. If you have a contrast potentiometer already connected just turn it all the way down to see the single line of blocks.
If the LCD still looks like that after the MCU has supposedly configured the LCD, then the configuration was done incorrectly.
You have connected a contrast potentiometer I take it - and tried to adjust it? If not then that will be a problem.
There's not much else you can do to test it, other than connect it to a known-working controller.