Look for a partner, not a vendor. You want a CRO firm that understands how your business operates, your goals, and your audience. Check their experience, review their previous projects, and ask how they run tests—do they start with research or jump straight into design? Do they handle dev work, or is that on you? Clear reporting and communication are a must. You should know what’s being tested, why, and what impact it had. And don’t forget cultural fit. If they don’t get how your team works, collaboration will feel like pulling teeth.