OK, so you've got a manuscript and you're pretty happy with it. You've done the first rewrite, or the 3rd rewrite or the15th rewrite, and you're satisfied with the motivation, dialogue, character development, story arc, action, denouement. What now?
1) Beta Readings
What is a beta reader? A beta reader can be anyone you trust to read your manuscript and give you useful feedback. It doesn't have to be a professional writer or an editor. In fact, it's a good idea to have at least one beta reader who is just that, a reader. Someone who loves to read, reads a lot of books (preferably in your chosen genre) and who isn't afraid to give you the unvarnished truth. Generally your mom or your significant other or your best friend is not the best beta reader. They're apt to tell you that whatever you wrote is the absolute bee's knees. That's not always the case. My best friend is a great beta reader because she will tell me in no uncertain terms if what I just wrote is a load of crap, and she's usually right. So be judicious in asking those close to you.
But it's a good idea to find and connect with other readers who aren't so close to you, but are willing to take the time to provide this service. Where should you look? Writer's groups, improv groups, forums, message boards. Get to know people (either in person or online) and find people you trust to evaluate your manuscript as a whole. Offer to trade services. A great way to do this is to trade manuscripts and act as reciprocal beta readers.
For our first mystery Darker By Degree, we were lucky enough to get input from two publisher's reader groups. Beyond that, I've met some great people online and traded manuscripts with two of them. Both of those readers mentioned the same two plot points or motivations as things they "didn't quite buy." After looking back at those segments, it was obvious what they had found, and we're working to fix those things in a final rewrite.
2) Copy Editing and Content Editing
While "copy editing" in it's strictest sense is practically the same thing as proofreading, I'm combining copy editing and content editing on a continuum, because it's best to find one person who can serve as an editor and hit these basic needs.
And editor is going to pick your mistakes, the ones you pass by. And trust me, no matter how careful you are, you will pass them by. I've made my living as a proofreader and editor and I'm damned good at it, but when it comes to my own stuff, I can't see things the way I see it in other's work. It's human nature. And while if you are a crack editor you can catch 95% of your errors, there's still room for improvement. And if you're not a crack editor, you damn well better find someone to check you. It's vital to not end up with a sloppy manuscript.
A good editor will not only find your grammar errors, but will find your structural and style errors. Do two characters have indistinguishable voices? Are the names of characters too similar? Do you use the same imagery too repetitively? Is your action unclear, your opening weak and uninspiring? I could rattle off a hundred other things, but you get the drift.
I'm lucky and know people who will edit me for free, in exchange for my editing services on their work. If you are at sea and don't have someone you trust as a professional, you may need to hire an editor, which can be expensive. Again, if you're going DIY, the best thing to do is barter services with someone. On the upside, the longer you do this, the better you yourself get as you learn to look out for the things that trip you up.
A proofreader is going to catch your spelling, usage, punctuation, capitalization, agreement, typos, and basic formatting errors. A good proofreader will make sure that style is consistent, i.e. that sometimes you don't write two o'clock and at other times write 2:00. At the end of the process, you should have a clean manuscript. A proofreader does not "edit," per se, but makes sure you're manuscript is consistent in usage and free of typos. Make sure you use someone with experience, even if they're a friend. You'd be surprised at the common misconceptions that abound about usage and grammar. Make sure they use an industry standard guide, such as the AP Style or the Chicago Manual of Style. Or if you're doing it yourself, make sure you've brushed up on your basics and have a reference book if you have any questions.
I'm using formatting here as a distinctly different step from typesetting, which we'll get to in the future. (Different publishing platforms require different formats, i.e. PDF, Word, HTML, each with their different typesetting requirements and quirks). When I'm talking about formatting, I mean your basic margins, chapter headings, indent length, scene breaks, font, etcetera. You want a consistent manuscript style. The more consistent and careful you are in formatting your manuscript, the easier it's going to be to typeset it and move it between programs.
I usually do the formatting myself and have someone else go over it, particularly my significant other, who is good at picking up inconsistencies.
While you're working on getting feedback and shepherding your manuscript through these stages, it's time to move on to choosing your publishing formats and working on your marketing, but that is a tale for another day. Back to my own rewrites...