It's always the ones you least expect.
I've heard the same story so many times from sales guys: Some guy wearing dirty old clothes comes into the dealership and is ignored by one salesperson, and when he comes back the next day in a suit (because he's actually filthy rich but likes to mow his own lawn for sh!ts and giggles) he gives his business to someone else who didn't pre-judge him.
Now, I can pretty much tell who's going to be a total knob to me from the next display over. I can see it in the expression on your face when you're talking to the other brand's booth babes, by the way you carry yourself. And yet, I refrain from judgement (outwardly at least) and talk to you anyway in the same friendly way I do the non-knobs, until you piss me off. And even then I just end the conversation and walk away. I don't even punch you in the junk!
Point is, I don't judge a book by its cover because on rare occasion the pre-spotted knobs have turned out to be cool. And the lady you think will only be interested in vanity mirrors and cup holders may have a nascent need for speed that only you can help develop.
I love it when a woman pushing a stroller asks me to compare torque numbers within our lineup.
I love it when a 7-year-old girl rattles off more technical specs than a Detroit engineer.
I love it when I overhear Grandmas talk about the "real" purpose of rear seat privacy shades (naughty Grandma). It's always far less creepy than when Grandpa does the same.
I love it when I shock the hell out of some know-it-all by, well, knowing it all.
Don't assume, kids. Ass. You. Me. Etc.