- deliver your book on or before the agreed date
- deliver the book that was commissioned and make sure it's finished (ie as good as it can be).
If you can't do both of these, ask your editor in advance which is most important to them. Should you send a less-than-perfect draft on time, or can they give you a bit more time to perfect it? If they can, you must perfect it by the next agreed date.
Whatever other compromises there are, you must deliver your book in a format the editor is happy with. This is likely to be a Word file, sent by email, though I have worked with a couple of publishers since 2000 who still wanted a printed copy (as well). Within the Word file, they might want something very specific - eg Times 12 point double-spacing with two-inch margins, or whatever. There is a reason for this, so if they specify it you must do it. The reason is not that they are boring old farts with no appreciation of your artistic formatting skills. It's that they know how to judge the length of a manuscript in their specified format. (This is less important when they can just look at the word-count in Word, but old habits die hard.) If you're working with a freelance editor or a small publishing company, it's often best to save your file in .doc format rather than the newer .docx format. It wastes time if the editor has to come back to you because she can't open the file on her antiquated computer system.
Deliver your book with a brief, polite email. Don't apologise for anything in your book. If they are going to find faults, they will find them without you pointing them out. And certainly don't say 'I'm sorry chapter six is a bit thin - my son was sick, and...'
If you know the editor well, you can be a bit chatty - ask after their children/holiday/health. Don't give a run-down of all the problems in your life even if you do know the editor well. It's not professional. What you should do, though, is alert the editor to any forthcoming events that will mean you're out of contact if they have any problems with the file or the book. So 'please check that you can open the file, as I won't be around for the next couple of days to resend it' is fine. Or 'I'm going to Borneo for three weeks next Wednesday so I'll be out of contact...' This is helpful information - if you don't tell them, you might hold up production of your book by several weeks and that won't be popular.
But really there is only one thing to say about delivery of your book: deliver your book, as agreed. No excuses, no crap, no delays, no 'corrupt files', no decorative effects, no pages stuffed in jiffy bags (unless specifically requested). Simple.