One thing I've been told is never edit while you're creating. Get your thoughts down, and then when you're finished go back and edit. That may take several passes. The first pass may be for continuity. Make sure the places and characters' names are spelled the same way throughout, or make sure you didn't change someone's name mid-story. It happens. If your main character has blue eyes when the book starts, keep them that way or explain why they changed color. You're the author, you can fix it.
Spell check doesn't check everything. Make sure the word you wrote is the word you meant. To, two, too or assure ensure. There are more. You know them, don't confuse them. Spell check won't correct words that are spelled correctly even if they aren't the correct word. If you want the word 'and' and you forget the 'd', 'an' is correctly spelled. Proof reading aloud will catch those errors.
Grammar. You say, "Ugh." I understand. Use the Chicago Manual of Style. The ruled have changed and seem to change annually. Keeps grammar books selling. Even dictionaries have a variety of ways to spell the same word. Some grammar practices 'date' an author. Some rules are old school today and publishers have moved on. Read. See how the publishers are editing the type of book you're writing. If they use serial commas, I'd suggest you follow that practice.
Ebook publishing has changed the way the industry does everything, from contracting to promotions. Keep up with the trends. At a later date, I'd like to take each topic and break it down for a blog.