Work in house first. That’s the best way to learn all you can about editing and proofreading and make good connections. I have met several people I’ve worked with from hanging out in Twitter and responding to tweets asking for an editor or proofreader, but I have had the most success from business connections I made while working in in house. Other things – a web site, professional associations such as the SFEP and the EFA (though I can’t say much more on these as I am not a member of either yet!), social media.
I’m sorry you had a bad experience on Fiverr. I feel like their cheerleader right now but I know there are some terrible sellers there … always have been. You can’t even always tell by the gig description because some sellers simply copy the description of someone else. But reviews do not lie. Hire someone with no fewer than 500 reviews, I would say, and all positive.
I have over 25 years of cumulative experience as a technical editor, proofreader and writer. In addition, I can add another 8 years to my resume acting as the head of a corporate word processing division and also as an administrative assistant. I am an expert in the use of MS Office (Word, Excel, Powerpoint, Outlook), Adobe Acrobat and equation entry/editing using Word and MathType. I have extensive experience formatting and laying-out text for publication.
It’s always sensible to follow due diligence in submitting your first draft of your book to an editor by making as fool-proof a copy as possible for you because first, it is your own creation, and secondly, a horrid draft sent your editor can end up frustrating both you and him or her. Make your own corrections to the extent you can, so that will make the job of your editor that much lighter and the end result would be a lot more effective.