Each book project is different and I can advise on what you need to think about for your cover, the blurb on the back, what to have in your preliminary pages and in what order, what legal info you need. You may be so keen to get on with the story (good!) that you miss some inconsistency – for example, don’t have the body on the lawn found face-down and then note that no-one recognised him; or have your child hero transported to an icy land and have them dig their hands into soft earth; and if someone’s in a backless evening gown don’t have them pull their collar up! (These are all real examples!) Also little things like someone coming into a room and shouting, then getting up. But they are already up! As for the shouting, bear in mind the golden rule, ‘Show, don’t tell’. Your skill will tell the reader that the character is angry, for example, without you having to state that fact. The other golden rule in writing is to ‘Avoid clichés like the plague’!
Another thing that sometimes happen is that during one of your many revisions you’ll add in something, perhaps a duplicate paragraph, or you’ll refer to something that doesn’t happen until later in the book (very common!). But these are things that I, as your copy-editor, will spot. (A proofreader, strictly speaking, is someone who checks the ‘proofs’ ready for publication, so will only flag up spelling errors and other small changes – all the other changes, to grammar, for example, should have come at the earlier copy-editing stage, sometimes also known as line editing or developmental editing.)