The SEO agency market is saturated. For every agency that delivers genuine, compound organic growth, there are ten that promise page-one rankings in 30 days and disappear with your monthly retainer. Knowing how to tell them apart is one of the most important decisions a marketing leader can make.
Start with your goals, not their services
Before approaching any agency, define what success looks like in measurable terms. 'Better SEO' is not a goal — 'increase organic-attributed leads by 40% in 12 months' is. The clearer your target, the easier it is to evaluate whether an agency's proposed strategy will actually get you there. Agencies that agree with vague briefs and promise results without asking hard questions are usually selling confidence, not competence.
What to look for in an agency's track record
Ask for case studies from clients in your sector or with comparable website authority. Look for specifics: which keywords moved, how much traffic increased, and most importantly, what happened to leads or revenue as a result. Generic 'we grew organic traffic by 300%' claims without context are meaningless — traffic from irrelevant keywords has zero commercial value.
- Client references you can actually call — not just written testimonials
- Vertically relevant case studies (a B2B SaaS agency case study is not evidence for an eCommerce client)
- Before/after ranking data for competitive, transactional keywords (not just longtail)
- Evidence of link acquisition — domain authority of links earned, not just volume
- Client retention rates — good agencies keep clients because they deliver results
The right questions to ask in a pitch
A structured pitch process reveals how agencies actually think. Send every agency the same brief and compare their responses. The questions that separate good from great include:
- What would your technical audit of our site reveal in the first 30 days, and what would you prioritise?
- How do you build links — describe your outreach process and the types of sites you target?
- Who specifically will work on our account, and how much of their time will we get each month?
- How do you measure SEO success, and what will your monthly report show us?
- Can you share an example of a strategy you tried that didn't work, and how you adapted?
Red flags that should end a conversation
The SEO industry has a persistent problem with bad actors. Some of these are obvious; others are subtle enough to fool experienced buyers.
- Guaranteed first-page rankings — Google explicitly states no agency can guarantee rankings
- Ownership of your content or links — you should own everything created for your site
- Black-hat link building — Private Blog Networks (PBNs), link farms, and paid link schemes can result in manual penalties
- Lock-in contracts without clear performance milestones — good agencies don't need to trap clients
- Unwillingness to share who works on your account — vague 'our team' responses suggest offshoring to low-quality freelancers
- Reporting only on rankings, not traffic or conversions — rankings are a means to an end
How to evaluate an SEO proposal
A good SEO proposal should clearly articulate the current state of your site, the priority areas for improvement, the proposed strategy for each (technical, content, links), timelines with realistic expectations, and a clear reporting cadence. Proposals that focus entirely on deliverables (number of blog posts per month, number of links per quarter) without connecting those deliverables to business outcomes should be treated with scepticism.
Pricing: what you should expect to pay
Quality SEO is not cheap, and cheap SEO is almost never quality. UK agency retainers for meaningful SEO programmes start at around £1,500–£2,500/month for small businesses and scale to £5,000–£15,000/month for competitive sectors or larger sites. If an agency is offering comprehensive SEO for £500/month, ask yourself what they can realistically deliver — content research, writing, link outreach, and technical development all require real time and skill.
Making the final decision
Once you've shortlisted 2–3 agencies, your final decision should factor in chemistry as much as capability. You'll be working closely with this team for at least 12 months — do you trust them, do they communicate clearly, and do they feel like a genuine partner rather than a vendor? The best agency relationships are collaborative; the worst are transactional. Choose a team that challenges your assumptions as well as supporting your strategy.