Never skim on editing your book. Few things feel worse than opening your freshly published book, only to see errors grin at you on every other page. Yes, you will find an error or two in your manuscript in spite of endless editing. Human error is here to stay. However, you want to keep the number of typos as low as possible for the best impression on your readers.
To avoid having multiple errors in your book, edit it – not once – but three, four or even more times. You don’t have to spend a lot of money on this, but you will have to put in the effort and get others involved in the search.
A good practice for authors is to do the first two edits themselves. Go over your work once with a wide tooth comb. Fix all the glaring mistakes and things that jump out at you immediately, such as poor spelling and punctuation. Don’t worry too much about grammar at this point, or your head will ache. Get the bigger lumps out of the batter.
Once you’ve done this light combing, go back a few days later and comb out the more subtle issues. Things like style, clarity, consistency, and phrasing. Remove needless words, and simplify complex ones, if you can. Take your time and fix all the hidden issues you can find. Crush those elusive small lumps.
After these two edits, your book will be almost ready for print.
Remember, this is your book. You spent days, weeks, and months pouring over these words. They are a part of you, and you are used to them. Your eyes may glaze over areas of text because you know what it says, or what it’s supposed to say. Somehow, for reasons unknown, you missed mistakes that you will never see, because, like the guy on the train who didn’t brush his teeth, you can’t smell your own breath most of the time.
This is the point where you get a second opinion. Talk to a friend, relative, coworker, or someone else who is willing to help and who you trust to give objective feedback. Ask them to read over your book and mark the issues they find. You should not have to pay at this point – find someone who is willing to just help you out. Listen to their comments, and have them use Track Changes in Microsoft Word to mark the errors they find. Accept the changes you agree with, and discard the rest.
You now have a solid manuscript. Your last step is to hire an editor.
Now, because you have cleaned up as much of the mess as possible, you can save money in hiring a language expert by asking them to only proofread to work.
Why? Unless you are horrible at grammar, you should feel confident that your writing is clear, concise and consistent at this point. By asking a book editor for proofreading only (which preferably would include some setting up of correct margins and such for the size you want to print your book in), they will only look for blatant errors that have slipped past your eyes. Since you are paying them to do their best work, they are not likely to slack a bit in picking through the material. They want your recommendation, and they will do their best to bring your manuscript as close to perfect as possible.
A good professional editor should offer you a sample of their proofreading or editing work at no charge, so that you can be confident that they know their stuff. They should also ask you about the book: its intended audience, its topic, if you have any personal writing styles that you know aren’t grammatically correct but don’t want changed, etc. The more they know about the work load, the more accurate their pricing will be, and you won’t have to worry about your book becoming the first chapter in a horror story of a box full of typo-ridden copies.