What Should Writers Look for in a Good Proofreader?

I recently finished a draft of my manuscript and realized how difficult it is to catch your own mistakes after reading the same pages many times. That’s why I started looking into book proofreading and understanding what actually makes the process effective. Some writers recommend hiring a professional book proofreader, while others rely on beta readers first. I’d love to hear from experienced authors here what helped improve your final manuscript the most, and what should beginners avoid during proofreading?
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Hi, I’m Jacob, publisher at Pyramid Writing Press. I help authors create engaging books and work with our book illustration service to bring stories to life.