It's called Social Proof.
Here's the thing: people are much more likely to believe what other people say about you than anything you say about yourself.
That's obvious, really.
So that's why I encourage you to include testimonials from happy clients in your newsletter.
Of course, in order to include those testimonials, you need to collect them in the first place!
So if you don't have a bunch of testimonials, consider making it a priority to collect positive comments from your clients. For example, whenever someone says something nice, ask them if you can use their words as a testimonial, ideally with their full name. And think about ways you can create a system to collect testimonials from clients – perhaps by asking them to complete a survey about your service.
The best testimonials are in your clients' own words so that they sound natural. They also include concrete details of how your service has benefited them. The more real they are, the better.
When you've got some testimonials, edit your newsletter and put them in.
It's a very simple way to add social proof to your business.
(This should go without saying, but don't even think about making up testimonials!)
Picture by Hans van Rijnberk