How can a customer leave me feedback?

If you are talking about online feedback through a website, I'd suggest Feefo or Hotjar. There are plenty of other solutions, but those are really easy to set up. You could also factor in customer feedback requests into any email marketing you are doing and this kind of thing can be automated through all the major email service providers.

There are a number of ways to get feedback and testimonials from customers and clients.

I have worked heavily in the Public Speaking industry for the past few years, i mention this because unlike some of the other industries I've worked with , here release so heavily on PR.

A few common ways are to use a rating section on your website to help for a wide cast net, or direct contact for more laser targeted approach. Typically if you pre frame the customer experience to end in a survey to acquire feedback you shouldn't have any issues.

If you do call me! I would love to help!

It'll be cool if you have more details about it :)

Are you a e-commerce, SaaS solution, service provider?

For each one, there're some approaches for it.

Besides, there's also the right moment to ask for it.

For example: If you sell products, you can use SurveyMonkey to ask for feedback some days after the user receives the product.

If you're a Saas solution, you can ask for feedback:

1-) Right after the user converts in your solution
2-) You can ask via call and ask for their permission to use.

It all depends from your solution and moment for using it :)

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/.