You've seen it a thousand times. 'Great to work with, would highly recommend!' It's the most common testimonial on the internet. It's also completely useless for converting new clients.
Here's why generic testimonials don't work: they tell new potential clients nothing they couldn't assume. Of course you're 'great to work with' — you wouldn't put a testimonial on your site that said otherwise. The claim is too expected to be convincing.
What converts is specificity. The before and after. The transformation. The detail so specific it could only have come from that client's real experience.
The one question that gets you a great testimonial:
"What was the specific moment you knew the work had made a real difference?"
Or if you want to go slightly more structured:
"Can you tell me: where were you before we worked together, what was the shift you experienced, and what's different now?"
These questions are designed to unlock story. Before, during, after. And story is what converts new clients — because it lets them see themselves in your past client's experience.
Timing matters too. Ask within 1–2 weeks of completing the project, while the results are fresh and the enthusiasm is still high. Don't ask at invoice time. Ask when they've just seen something working.
And make it easy. Give them the question in an email, tell them a few sentences is plenty, and give them permission to be casual. "You can write it like you'd tell a friend" often produces the most human, convincing testimonials.