When you get to China most websites like Facebook and Youtube will be unavailable for you as it is blocked.
To get around this you can pay around £60 for a years subscription to Astrill (recommended), a VPN (Virtual Private Network) that is pretty much guaranteed to work anywhere, anytime.
Or you do not need censored websites so much, you should try Freegate, it does the same job as Astrill except free. Note: it can be temperamental as it battles against being shutdown most days.
Getting a VPN is especially useful if you are working from your own computer as often websites used for work can be blocked, leading to hours getting stressed at your computer!