The reason this beats every other method is evidence. Ideas generated in a planning session are guesses about what somebody might want. A question that arrived from a real prospect, in their own words, at the moment they were deciding, tells you both the topic and the phrasing. One is speculation and the other is a request.
Go through the last three months of correspondence rather than trying to recall the questions, because memory smooths them. Mark anything that was asked, anything you explained at length, and anything that preceded either a sale or a decision not to buy. The list produced that way is invariably longer and more specific than the one produced by reflection.
Pay particular attention to what came up just before somebody bought and just before somebody did not. Those are the questions with commercial weight, and they are frequently about cost, comparison, timing, or what happens if something goes wrong rather than about the thing you sell. Answering them publicly means the next prospect resolves it without a conversation.
Ask directly as well, since customers will tell you if invited. A single question at the end of a project asking what they wished they had known at the start produces answers that no amount of analysis would. Five of those responses is a content plan.
Look at the searches that already bring people to you, which is available in your search console and almost never consulted. The queries where you appeared and nobody clicked are particularly informative, because they show what people were looking for alongside evidence that your page did not satisfy it.
Watch what your competitors are asked rather than what they publish, which is visible in their reviews, their social comments, and their question sections. Those contain genuine customer language about the category, and they surface concerns that your own customers may share without raising.
Be careful about keyword tools as a primary source, since they describe volume rather than intent and they systematically favour broad informational terms. Those attract readers who are learning rather than deciding, and a business writing for them accumulates traffic without enquiries.
Keep the list somewhere you can add to in seconds, because the moment a good question arrives is rarely a moment you are at a desk. A note on your phone works better than a well organised document, and forty rough entries is worth considerably more than six polished ones.
Then notice which pieces produce responses, because the pattern is instructive. The material that performs best is reliably something you considered too basic to bother with, and that reaction is the clearest signal that you are underestimating what is worth explaining.
Write down the question in their words rather than translating it, since the phrasing is half the value. A question recorded as somebody actually asked it becomes the heading, and that is frequently what somebody else types into a search.
Revisit the list quarterly rather than working through it in order, since the questions arriving change as the business does and a plan written six months ago describes an earlier version of your customer.
Notice which questions arrive from people who did not buy, since those identify the objection that is costing you work. Answering it publicly reaches everybody holding the same hesitation silently.
Keep the answers you write, since a reply composed for one customer is a draft for everybody with the same question and rewriting it from scratch later wastes the thinking already done.