Has anyone tried negotiating cheaper rent? How'd it go?

I honestly didn't know you could negotiate rent until a couple years ago. I imagined it wasn't really possible here as the demand on rentals is through the roof, but I recently learned that someone I know was successful. He's a 24 yo clean cut guy with a decent job but nothing special really. He negotiated with one of those new build apt buildings so I doubt he offered additional house maintenance or anything. Also, he signed a 6 month lease so it wasn't a longevity thing. I don't understand what he offered besides a good credit score. It's making me wonder whether I should just try in the future lol.

Have you guys tried? Was the landlord/property manager offended or annoyed at you for trying? If you were successful, what do you think made the difference?