I have found that a large number of people looking for editorial services are actually not 100% clear about what type of editing they require, so I thought I would do a real quick breakdown concerning the differences.
This is the big picture stuff! Your editor will read the novel, and make sweeping suggestions as to what you could change to improve the story.
This can involve: plot, pacing, characterisation, number of characters, scene placement and requirement, chapter development. You should receive an editorial report that works through areas of improvements. This is the type of edit where you’ll most benefit from a phone call (or Skype session) with your editor, so that you can explore exactly what the editor meant and offering possible new directions to gauge their reactions.Some editors will offer this as part of their services, so it’s definitely something you should check when approaching them.
This type of editing is very specific, and requires a unique set of skills from your copy editor. In this case your editor is going to check things such as: continuity (do your characters have the same spelling for their name, the same hair colour, the same eye colour); address/phone number checking (to make sure you haven’t accidentally used an actual address or phone number in a fiction novel); grammar and sentence structure (looking for frequently used words, for example). One of the best copy editors I know has checked phases of the moon according to the dates that featured in a fiction novel, to make sure that the full moon mentioned was accurate; and has offered technical knowledge about whether that murder by strangulation was given the correct amount of time.
This is the last check before publication. This is the final opportunity to check for any errors, such as issues of homonyms, errant punctuation, and formatting problems. You need an eagle-eyed proofreader with access to a chosen house style/recognised manual of style (my preference is the New Oxford Style Manual). They won’t just make sure that your spelling is correct, but sort out your hyphenation and your number styling.
These days self-publishing is a valid and recognised option on the route to getting your novel in the public domain, but you need to invest to ensure it is as strong as possible. And this also means making sure that you are hiring the correct person to work on your novel.