It would be best if you did not take your personal laptop. Get a cheap chromebook and put your important data on a cloud service of some sort. Once you pass through customs you need to completely wipe the laptop, re-install a trusted version, then pull down the data you need. Wipe the laptop again before you leave and be prepared to just leave it behind if it ever left your physical control during your trip. Find out which VPN services are currently working from China and also familiarize yourself with shadowsocks.
You need a disposable phone that does not have any data on it (contacts, notes, photos, etc) that you do not want to share with the Chinese government. If possible you should get a SIM card from Hong Kong and use that since it is less likely to have VPN and other connections blocked.
Beyond this you should look to some of the online guides out there targeted at journalists and how they can protect themselves, most of the same rules will apply to you in this situation.