Protecting your data, protecting yourself: A first installment

Let's say—for whatever reason—you're concerned about keeping your communications safe from government prying. Assuming you aren't a high-profile target to warrant direct hacking (the United Arab Emirates allegedly tried to breach the digital defenses of human-rights activist Ahmed Mansoor on three occasions, for example), there are reasonable measures you can take to live a normal life and continue to have private thoughts and private conversations.
Note that I'm not singling out an