Build the prompt set first
Twenty to thirty questions is plenty. Mix category questions (best X for Y), comparison questions (X versus Y) and problem questions (how do I fix Z). Write them the way a buyer would rather than the way a marketer would.
Freeze the list. The value is in the trend, and changing your prompts every month destroys the trend.
What to record
For each prompt and each platform: were you mentioned, were you cited with a link, which competitors appeared and what the model said about you. That last column matters most. Being mentioned inaccurately is worse than not being mentioned.
Run it monthly. Weekly is noise, quarterly is too slow to act on.
What to do with the data
Where a competitor appears and you do not, find the source the model cited and work out why they are in it. Usually it is a listicle, a review site or a comparison page you are missing from. That becomes your PR and outreach target list, which is how AI visibility work turns back into online PR.