24-hr layover in Shanghai - I'd like to explore and leave the airport

I'm travelling to Manila from Toronto, with a 24hr layover in Shanghai. (Toronto > Shanghai > Manila)

I'd like to do some exploring and leave the airport during the layover, so:
- Do I only need to fill out the Arrival/Departure card or is there anything else that's needed?
- If so, do I need to fill it out twice: when I leave the airport and when I re-enter?
- Where do I request a Arrival/Departure card - when I check-in with the airline in Toronto? On the plane? Or when I touch down in Shanghai's airport?

Thanks.