... unless this person is a cannibal who intends on eating me.
Then, screw that. All bets are off.
Phase I, among co-equal unknowns: Do unto others AS you would have them do unto you.
phase II, among those proving themselves less than trustworthy: Do unto others AS they do unto you.
phase III, among those who have demonstrated predatory behavior: Do unto others BEFORE they can do unto you.
Of course, it would be preferable to avoid those covered in phases II and III rather than to manifest THEIR behaviors with them ... if one has the luxury to avoid those behaving inconsiderately and/or predatorily.