The answer really depends on what your client prefers, whether that's replying to a survey, posting on social media or chatting live on your site.
If you have a product you want their feedback on, try the Likert scale. The Likert Scale is best used to measure and evaluate customer sentiment on a specific product, service or experience.
Likert items that center around the same topic should be grouped together in your survey, creating what’s called a “single-topic” Likert scale.
The scale itself, regardless of whether it uses numeric or text labels, should be consistent on each item; this prevents confusion for your customers and simplifies the analysis of their answers for you.
The most valuable Likert item sets include additional questions that capture open-ended feedback to tell you more about why each customer chose the answer they did.
Here's how to use this scale to collect customer feedback: http://www.fieldboom.com/blog/likert-scale/.