Use a nice sharp blade and not only follow the flat surfaces such as the cheeks and bridge of nose, but the corner of eye to ear. Bigger dogs have bigger poodle swirls. When you think you are DONE, go back with your hands and check the swirls and make sure you didn't miss some. Alot of times, I see areas on my own dogs that I missed. I notice it alot about a week after shaving....and I think "How the heck did I miss that spot?"
I use a #15 blades AGAINST the hair, so up from the chest on the neck, down the muzzle, toward the eye from the ear. And you have to pull the lip back nice and tight to clean up the inside of the lips perfectly.