"If you are very nice and we like you, we can upgrade you to a better room or a suite at no extra cost, if there's any available.
Different hotel brands have different policies when it comes to upgrading their guests. The hotel I worked at didn't really care, as long as we had the availability we were allowed to.
I did have some guests who asked for free upgrades, if they were nice I'd give it to them, if they weren't I'd lie and tell them we didn't have any suites available."