Okay, so you managed to push through your bouts of writer’s block and finished the rough draft of your manuscript. Awesome. Savor that feeling. Because that was the easy part.
The next thing to do is self-edit. I would suggest going through your book at least three times, checking for spelling, grammar, and continuity issues. Make sure your characters aren’t speaking with the same voice. Also, keep an eye out for other problems such as an overabundance of adjectives and overuse of particular words.
Next, find some beta readers. These can be either fellow writers or readers–preferably a combination of both. Either way, make sure you’re confident they will give you an honest opinion. Measure the responses as they come in. If more than one person is bringing up the same point, it’s probably a good idea to address it. If only one reader finds a problem (and you’re a little dubious), put the issue to the others and ask their opinion. And no, you should never have to pay a beta reader.
Now, you need to find an editor. I won’t lie to you; good editors are pricey. A novel will probably run you a few hundred dollars. That said, this is not a step you can skip. There are minor grammatical issues a skilled editor will pick up on that went completely over your head, as well as words you’ve overused without even realizing it.
Finally, go over your work one final time. You can also hire a proofreader if you’re unsure of your ability to do the job or just want another set of eyes to assist you. This is your last chance to catch any mistakes, so make damn sure the manuscript looks the way you want before sending it out into the world. Because even if you missed something, I guarantee you there will be readers out there who won’t.