A lot of what I’m saying at the moment arises out of my work on the second novel in the Flight of the Kestrel series, currently called Adept. [Later Alien Secrets)
In the past I have written about how to give a critique, as it’s definitely a skill to be learned. But it’s also important to know how to receive criticism too. 
It’s vital you put together a team who will read and critique your work, preferably while it’s in progress, to guide you in the development of your story. These people may be your beta readers too, reading the finished book, or you may prefer to use other people. Critiquing excerpts is a very different task to critiquing a whole book.
It needs to be a team, because you want to have a spread of opinions. People have personal preferences and opinions that you might not agree with, so you need a critique from several people to see which points they agree on.
For example, I start Adept with three of the Kestrel crew in a cell, having been captured on a spying mission. When I shared my first chapter with the Feedback Group one person wanted me to start with the capture. I really didn’t want to have to write that. But the others in the group thought the starting point was good. So I might have done all that extra work, and hated it, if I had only the one opinion.
Critiquers will spot things you can’t see, tell you where things don’t work, and may even make some useful suggestions. In our Feedback Group (part of the Swansea and District Writers Circle) we discuss our critiques once a month, so things are clarified and we often toss ideas around to find solutions. If you can’t find a team or a Writers Circle, there are online communities like Critique Circle.
The last point I want to make is to remember it’s your book. You don’t have to take anyone’s advice when it comes to the story, but do give all comments serious consideration. You should take all advice on spelling and grammar of course.
There is no right or wrong in writing a book. There is only a puzzle, a question, of exactly what book you’re writing. This process of hearing critique will be a kind of divining rod. You’ll use the knee-jerks you experience to figure out what advice to keep, and what to throw away. Don’t listen to other people. Listen to you listening to other people. You may need to rewind that conversation periodically, and process it in your head, over and over. But you’ll get there. Writing takes a lot of confidence and energy. Revising takes humility and calm. — Laurel Snyder, author
Ann Marie Thomas is the author of four medieval history books, a surprisingly cheerful poetry collection about her 2010 stroke, and the science fiction series Flight of the Kestrel. Book one, Intruders, and book two Alien Secrets, are out now. Follow her at http://eepurl.com/bbOsyz