My critique group hears every chapter of whatever book I happen to be working on. They are invaluable at catching words and phrases I use far too often. And they remind me to put in things I gloss over. One member of the group always wants me to make moments between my heroine and her husband more tender, another reminds me to attach a color to clothing and objects.
Once they've heard the whole book and I've worked on each chapter, I print it out and go over it carefully. Amazingly, I find more mistakes and inconsistencies. Sometimes doing the fixes contributes to more typos, extra periods and two words used that mean the same thing.
With my latest that I'm getting ready to send off to the publisher, I've had a bit more problems than usual. A friend who has read all the books in the series offered to read the manuscript and point out anything she found. When she sent it back, I couldn't believe how much she found that I need to address. It's like gremlins attacked it when I sent it over the Internet.
Fortunately, the publishing house has a great editor. It will be interesting to see what she has to say.
Sometimes I wonder why I spend so much time writing, especially when I find so many mistakes. But, what would I do with myself if I didn't write?