[header] How to open a cat's mouth [title] Pick a time when your cat is at ease. [step] Don't try to open your cat's mouth when it is riled up, playful, or upset. You should also avoid waking your cat up to open its mouth, as it could scare the cat. 
Instead, just pick a time when the cat is calm and happy and wants to be around you. [title] Plan how you will position yourself and the cat.