How do you write a hint text?

Could you please explain the process of writing a hint text? I'm curious to know how to craft a concise and effective hint that guides users without giving away too much information. What elements should I consider when writing a hint text, and are there any best practices I should follow to ensure it's effective and user-friendly? Additionally, how do you ensure that the hint text remains relevant and useful as the application or system evolves over time?