The main one is having a voice to read my work back to me. I can't tell you how much this has helped me when editing. To hear your words spoken aloud, not by yourself, who will tend to read whateer your brain thinks should be there, but by an outsider who reads what is actually written. I use TextAloud, software that you can adapt to have a voice of your choosing. I chose AcapellaRachel22. She sounds like the sort of person I imagine reading my stories; like me, I guess. She has an English accent, so it is familiar to me and she will read my writing the way I hear it in my head. Don't get me wrong, she has her funny times, when the intination is completely wrong for the sentence I've written, but mostly it serves me very well and I pick up all sorts of errors I would have otherwise missed and I also hear clumsy sentences as they are spoken. Rachel is a good friend. She points out my errors without any criticism.
The other thing I want to tell you about today is a cleaner for the keyboard. I discovered this slime that you roll across your keyboard and it picks up all the fluff and dirt brilliantly AND it's just like the stuff you played with when you were a kid. What more could you ask for? Only one word of warning: don't let it sit for too many seconds without moving it, or it'll ooze all over your computer!