Ask HN: How can users protect their personal data?

In the wake of the Cambridge Analytica debacle, I've had several people I know ask me what they can do to protect their personal data and guard themselves against manipulation and "psychographic warfare". I've worked, in the past, on similar projects using big data and marketing automation so I think I take a lot for granted as far as what other people may or may not know about how to protect themselves online. Surprisingly, many people don't even know to check for https before entering credit card information!

I'm working on compiling a cheatsheet of tips to share with non-techy people when they ask me. There are obvious answers like "don't post personal information online", but I'm looking more for ways people can exist and operate reasonably within modern society while practicing good habits - something like "use different email addresses for every account" or something to that effect.

Curious to see what the ethos has to say!

Thanks!