Choose a useful mix
Select customers with different relevant situations, not only those most likely to compliment you. A project with a difficult starting point may explain your work especially well. Ask permission to discuss it and be clear about what you hope to publish.
Let the customer answer
Ask what triggered the search, what worried them, what alternatives they considered and what gave them confidence. Ask about the work and what changed afterwards. Avoid supplying the answer in your question. An interview can reveal something to improve as well as something to quote.
Keep the evidence behind the words
Save the original feedback, agreed attribution and publication permission. Check project dates and any numbers against a named source and reporting period. Distinguish an observation from a measured result. Never turn one customer’s experience into a guaranteed outcome for everyone.
Make two useful versions
A short testimonial can answer one concern beside a service. A case study can explain the situation, decisions and delivered work in more detail. Use a faithful excerpt and keep the full context. The Articles hub has a five-point testimonial checklist and a practical case-study guide.
Keep it relevant
Review permission and accuracy before reusing old material. Label historical projects and former arrangements honestly. Do not imply a former customer is a current client. Ask about a separately scoped proof-collection project if you need ongoing help; no old interview counts or standalone prices are promised here.