How to Choose the Best Book Cover Designers?

I’m searching for reliable best book cover designers and wondering how to pick the right one. What should authors look for in terms of style, experience, and portfolio? Are there certain design elements that make a book more appealing to readers? How do you balance creativity with market trends when selecting a designer? I’d love to hear tips or personal experiences from authors who have worked with top book cover designers and achieved a standout final product.