If you are planning to use a 16×2 LCD display with i2c controller in Arduino, check out this page for the three general types of LCD i2c controller, and the settings for each one of them:
https://arduino-info.wikispaces.com/LCD-Blue-I2C
Also, some controllers will have brightness controllers which can be adjusted using a small screwdriver. If the LCD blinks as per the code in the above site, but you cannot see the characters, it most probably is a brightness issue.
Cheers
Amitabh Kant 