A large spudger helps in the tough cases. Sometimes if the screen is cracked the suction cup doesn't suck (hmmm...it does but in a different way). There are even instances where the screen is on good -debris, wax, etc. Can all get lodged in between the front panel and bezel making the task a bit daunting.
Be advised, there is a risk of damage to the rubber gasket if you pry against it. Do it once and right the first time to keep damage minimal and isolated.
Good luck!!