Overall structure and formatting firstly. My old one was pretty 90s.
For the actual content, I filled out some questionaires about what make actual work history was, with too much detail so they had a base to work with.
They also made me send over some job postings that I thought I fit, and basically we went bullet by bullet saying things like "it really looks like you did this in your previous job, but none of what you gave me tells that story specifically. Would it be fair to rephrase this bullet as xyz?"
And then we just iterated that for a few rounds until we were all happy.
Technically, I could have done all that on my own following guides on the internet, but having an expert who has done this already call me out on everything was of great value to me personally.