The short answer
Choose the provider that can explain your search constraint, the work they will own, the evidence behind priorities and how results will be verified. Reject guaranteed rankings, anonymous case-study numbers and fixed link quotas.
Start with the business decision
A credible provider asks what a valuable customer action is, which offers and markets matter, what the website can change and what data can be trusted. If the conversation starts and ends with keyword positions, the commercial context is missing.
Ask to see the operating system
Request a sample issue register, content brief, release check or reporting view with confidential information removed. You should be able to see how evidence becomes work, who owns each item and how completion is verified.
- Diagnosis before package selection
- Named deliverables and ownership
- Developer and editorial acceptance checks
- Reporting linked to useful customer actions
Verify every proof claim
A useful case study names the scope, source, comparison period and material context. A client logo alone does not prove the agency delivered SEO, and a percentage without a baseline can mislead.
Compare the relationship, not only the fee
The lowest proposal can be expensive when it creates content debt, risky links or implementation work your team cannot support. Compare capability, access, review effort, delivery ownership and exit conditions alongside price.
Use a short selection scorecard
Score diagnosis, technical depth, editorial quality, measurement, proof integrity, communication, implementation ownership and fit. Write down the evidence behind each score before deciding.
Primary sources used
External guidance is linked so you can check the current source and context directly.