The short answer
Start with the queries you already show up for. Search Console gives you real queries, real positions and real click data for your own site, free, and it beats any estimate a third-party tool produces.
Then widen with autocomplete, related searches and the questions your customers actually ask you.
The free sources worth using
| Source | Good for | Blind spot |
|---|---|---|
| Your search console | Queries you already rank for | Nothing you do not appear for |
| Search autocomplete | How people phrase things | No volume data |
| Related and people-also-ask | Adjacent questions | No volume data |
| Your site search logs | What visitors could not find | Only current visitors |
| Support and sales enquiries | Real language of real buyers | Not search-specific |
The fourth and fifth rows are the most under-used and the most commercially relevant, because they come from people already interested in what you sell.
Mine your own data first
- Export your queries from Search Console for the last few months.
- Find queries where you appear but rank poorly, with real impressions.
- Find queries where you rank well but get no clicks.
- Group them by theme to see where you have gaps.
- Compare against what you actually sell, and drop the rest.
Point three finds the cheapest wins. A page at position five earning no clicks usually has a title that does not match the query, which is a ten-minute fix.
What paid tools add
Volume estimates, competitor visibility, and keyword ideas for terms you do not yet appear for. Those are genuinely useful and they are estimates rather than measurements.
For a business starting out, free sources cover more than most people expect. Paid tools earn their place once you have exhausted your own data.
Judge intent, not volume
A query with small volume and clear buying intent is worth more than a large one with none. Someone searching for a supplier in your sector is a different prospect from someone researching a definition.
That judgement is yours to make and no tool provides it. It is also where most keyword-led content goes wrong, by chasing volume into topics nobody buys from.