Civil Service personal statements, how do you actually score highly?

I’m trying to get my head around Civil Service personal statements, particularly for applications and I’m confused about what separates a high-scoring personal statement from an average one.

What is the actual purpose of the personal statement? What are sift assessors looking for, and what aren’t they looking for?

I understand that you’re supposed to show the skills/experience relevant to the job, but how do you weave the Civil Service behaviours into it without the whole thing turning into a massive STAR interview answer?

For example, should you be explicitly saying things like “this demonstrates Delivering at Pace” / “I showed Making Effective Decisions”, or is it better to demonstrate the behaviour naturally through the example and let the assessor make the connection?

Also, how do people get into the higher scores at sift? Is it mainly about having really strong examples, or is there a particular structure/style that assessors respond well to?

And finally, what are the easiest ways to screw up a personal statement without realising it? E.g. being too generic, just repeating the CV, not answering the criteria directly, spending too much time describing the situation, etc.

Would really appreciate advice from anyone who has sifted applications or consistently scored highly on Civil Service applications.