It s impossible to imagine how the world s terrible spellers survived before the advent of computerized spell-checking programs. Mercifully, we don t have to. But you d be surprised to see what slips through spell-check, especially when it s being run by a tired author clicking ignore over and over and over again. Homonyms are a particular problem, as spell-check won t catch them which witch is which, indeed. Spell-check it twice, find a proficient speller to read it through, get it as good as you can, and your copyeditor will catch the typos that slip through the cracks.
Every publishing house has a house style.
House style dictates certain grammatical and punctuation preferences and which grammar books and dictionaries will be used as the standard for accuracy when issues arise. Your manuscript will be edited to conform to house style, so that the small details are consistent throughout. All these questions need to be answered once, noted, and the style applied throughout the rest of the book. A good copyeditor knows that those idiosyncrasies and rhythms are what make your writing distinct and alive. She strives to preserve your voice as much as possible while correcting for consistency, clarity, and accuracy.