What you should know about internet in China before you visit
If you have never been to China before, you should know that a lot of everyday websites and services we take for granted are blocked in China
The most prominent and useful sites blocked include: all Google services (search, Gmail, maps, docs, Youtube), Facebook, Instagram, Twitter, Wikipedia, Pinterest, Reddit, BBC, New York Times
Refer to this Wikipedia article for the most up-to-date list of banned sites in mainland China
What you should do:
Download and set up a VPN app on your phone and laptop before you go to China. Chances are you won't be able to download the app while in China
You may have read recent news reports about China banning VPN but there has been no change on the ground level from what I'm seeing. I know tourists and locals alike are still using VPN every day as of today (August 2018). There has also never been a single case of tourists getting in trouble for using VPN
However, know that even with VPN the speed of all of non-Chinese sites will be very slow. Even non-Chinese websites that are not banned are slower in China
I personally have always used ExpressVPN, which is cheap ($13 a month) and very user friendly, and still works in China to this day. You don't need to know any tech to set up this app. You can always Google "best VPN for China" to get the latest list
Where this applies to:
Just mainland China. Hong Kong and Macau do not have any internet censorship
If you plan to go to the western provinces of China, specifically Tibet and Xinjiang, VPNs most likely won't work there (VPN isn't technically circumventing the censorship, it's just a tolerated avenue to access non-Chinese websites by the government; unfortunately in Tibet and Xinjiang, the local government doesn't tolerate it, so VPNs don't work there)