Why is my LCD 16*2 is not displaying any characters, although all the wiring is correct?

Check out this tutorial on Adafruit. It will walk you through setting it up. In the tutorial they change the pins, which I believe is the issue here. Here is a snippet.

And change your pins:

LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

Recently I also faced similar problem, with connection as:

1=GND, 2=+5v, 4=11, 6=12, 11=5, 12=4, 12=3, 14=2, 15=backlight positive, 16=backlight negative

Solution: I just connected VEE (pin 3) of LCD to Ground (GND) without use of potentiometer as it worked.

What is connected to LCD pin 3? Pin 3 is the contrast V0 and needs to be connected with a 10 KOhm potentiometer.

Some LCD's need a negative contrast voltage, check the datasheet of the display.

If the contrast voltage is not correct the display will stay blank. I came across the same problem until i saw the negative voltage must be applied :-)