Friday open thread: internet rules to live by

Today marks a tentative return of the Friday open thread, although given how things have been going for the past few months, I think it would be unrealistic to suggest that these are going to be a regular occurrence. We'll see how things go.

Today's question is: what advice would you give someone who is just starting to use the internet in terms of sensible rules of behaviour to follow? Please feel free to interpret 'the internet' as broadly as possible in terms of spaces/platforms, and as usage for either professional/daily life/personal contexts or some combination thereof.

(For those who are new around here, my 'Friday open threads' are semi-regular posts where I pose a question, answer the question in the post, and anyone reading can answer the same question in the comments. Responding to other people's comments is also encouraged, should you so desire.)

( My answers )

What about you? Do you have any recommendations or rules for a harmonious internet life?