Testimonials can work very well if they're done right.
Don't plug testimonials just because you want to have them somewhere. Testimonials should be carefully picked.
A few things to consider,
Try to include testimonials from people your visitors will recognize. A testimonial from John the IT guy from XYZ is not going to make your visitors trust your brand. But a testimonial from a client working for a company that people will recognize is far more effective and builds trust.
Don't over do it, keep it simple. Don't overload your site with testimonials. Nobody is going to read all of that. Don't have testimonials which are very long. Your visitors should be able to grasp it quickly.
Pick the most effective testimonials. Don't pick testimonials which says the same thing. Pick testimonials which praise different aspects of your services.