Start with evidence. Ask for case studies with real traffic and revenue growth, ideally in your industry or a comparable one. If an agency won't show you specifics about how they've moved the needle for clients, that's a red flag. At Ottawa SEO, we run a 500+ domain portfolio specifically so we can show prospects what works in practice, not just theory. Verify their methods align with Google's guidelines. Ask directly: do you build private blog networks, buy links, or use AI content farms? Agencies using shortcuts might spike your rankings briefly, but you'll pay for it in penalties later. You want someone who audits technical SEO, optimizes existing content, earns links through outreach or digital PR, and builds authority steadily. Match their reporting to your actual goals. If you run a local business in Ottawa, you don't care about global keyword rankings—you care about calls, form fills, and foot traffic. If you're e-commerce, you need to see assisted conversions and organic revenue, not just sessions. Make sure the agency tracks what matters and explains month-over-month changes in terms you understand, not jargon. Evaluate communication and transparency. In the first conversation, they should ask about your business model, competitors, and past marketing efforts. If they pitch a one-size-fits-all package without understanding your situation, walk away. Good agencies tailor strategy to your specific constraints—budget, timeline, technical limitations, content resources. Finally, consider specialization versus generalization. A boutique agency that only does SaaS SEO might outperform a full-service shop if you're selling software, but a generalist with a strong portfolio can adapt faster if your needs shift. We've seen both work. What doesn't work: agencies that overpromise timelines (no one ranks in 30 days for competitive terms) or guarantee specific positions (Google's algorithm doesn't work that way). Trust the ones who set realistic expectations and show you the roadmap, not just the destination.