After the interviews you've got a pile of requests: facts you need, features, moods. You have to decide what to ask the client for, and what you can safely leave out. Get it wrong and the launch slips, usually waiting on something nobody needed.
That's the requirements list. Every request gets a tag, and every tag gets a reason in a few words. If there's no reason, it gets no tag.
BLOCKS START means you can't plan the site without it. Which services the business really offers, where it works, who the site is for. Get those wrong and every page after them is wrong. BLOCKS LAUNCH means you can build with a visible placeholder, but the site can't go live until the real thing arrives. Prices, real photos, the legal business name. LATER means it's a real request, worth doing, and outside this launch. It's written down with its reason, so the client knows they were heard.
Here's one for a fictional mobile dog groomer. Tomasz drives a van and books everything by text. Areas and services block the start, because the whole site hangs on them, including what he won't do. He doesn't take very large breeds, and the site has to say so. Prices, photos and his insurance wording block launch. Each sits in the build as a placeholder, marked so nobody could mistake it for the real thing. And the online booking calendar is LATER. Here's why.
In the interview his partner said, more than once, that they must have online booking. Said that firmly, it's tempting to tag it BLOCKS LAUNCH. That's the classic mistake: a wish tagged as a requirement because somebody said 'must'. Look at what actually happens. Tomasz books by text between appointments. A calendar he doesn't keep up to date shows slots that don't exist, which is worse than no calendar. So it's LATER, with the reason next to it, and with what would change it: the day he moves his diary into a booking tool.
Ask it of every item. If the answer is that the site can't do its one job, or that it says something untrue, the item blocks. If the answer is that someone's disappointed, it's LATER.
Then turn every BLOCKS item into a request list. That's what you actually send. Each line asks for one thing, in the form you need it. 'Your prices, exactly as you quote them by text' gets you real prices. 'Send pricing info' gets you a brochure from four years ago. 'Photos of dogs you've groomed, with the owners' OK' settles the rights question before it becomes a problem. Short list, specific asks, and a date.
An AI is useful here as an opponent. Once you've tagged the list, ask it to make the strongest case that the site could launch without each BLOCKS item. The ones it can't move are your real requirements. You still decide, and you write the reason.
The BLOCKS LAUNCH lines are your before-launch list. Copy them into the Go live checklist, so the site can't go out while any of them is still a placeholder. Every line is either real, or the site waits. How to search the built pages for a stray placeholder comes later, in the lessons on checking a build before it goes out.
Tag every request by what breaks without it, give each tag a reason, and send the client a list of specific asks.