Chinese public toilets come in two types: squat and western. Scenic areas, malls, airports and stations usually have both, with squats more common.
Using a squat: aim for the pit and squat; hold the front rail for balance. Loose trousers help, and watch your backpack.
Paper: many public toilets provide none, or only a communal roll at the entrance. Carrying a small pack of tissues is a Chinese habit - always have one.
Cost and hygiene: most public toilets are free (a few remote scenic spots charge 1-2 yuan); mall and metro toilets are generally cleanest.
Finding one: search "toilet/卫生间" on your map app for the nearest; malls have clear signage.
Special cases: some older toilets lack cubicle doors or working locks - check the latch before squatting; expect queues at scenic spots during peak hours.