Solo traveller in transit for 12 hours at Guangzhou Airport mid December. All suggestions welcome?

If you have to stay there at night, the best thing you should do is to find a nearby hotel to sleep.
If you stay there during the day time, you can apply for a 24-hour stay permit in the airport and go into the city downtown area to make a one day trip there. Haizhu Plaza, Yuexiu Park and Shamian Island are recommended for you.