My top tips are:

1. Don’t rush the process. Seriously! I know the lure to get your book out there, but if you don’t take the time needed to make your manuscript sparkle and shine, you will regret it. The best way you can force yourself to slow down is to put your manuscript into that metaphorical drawer for as long as practical after each editing/drafting round to give yourself as much distance as possible.
   
   
2. ALWAYS get another person to read through your work, and not just a family member or friend. Use other writers (and editors). Writers and editors understand the level of feedback you need to help you take your writing to the next level.
   
   
3. During at least one of your editorial passes, read your manuscript aloud. Not just a part of it, but the entire thing. And better still is to get the computer to read your story manuscript to you. It’s slow, but that’s the point. It forces you to focus on what is actually on the page, and not what you think is on the page. The ears pick up more than our eyes do.