How Do You Choose the Right Book Cover Designers?

I’m preparing to publish my first book and I’m unsure how to pick the right book cover designers. What should I look for portfolio style, experience, or understanding of my genre? How much impact does a professionally designed cover really have on attracting readers and boosting sales? Has anyone worked with designers who transformed their book’s appeal significantly? I’d love to hear recommendations or tips on selecting designers who can truly capture the essence of a story visually.