Keep it short.
That's one that always applies. In those cases where someone is genuinely interested, still, they are starting a conversation. Details should be given in conversation, not as a monologue. The initial answer should always be short.
As far as getting this question from strangers, sometimes I don't answer at all. It's a greeting, and responding with a different greeting works. Not always, but often. (And sometimes people say "How are you?" in passing and don't even wait for an answer.) I'm also quite okay with blatant lying, with strangers, when "fine" or "good" or such isn't a truthful answer. My thinking is that, in those cases, the true answer is none of their business anyway.
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not aspie, not NT, somewhere in between
Aspie Quiz: 110 Aspie, 103 Neurotypical.
Used to be more autistic than I am now.