I applied and was accepted into a writing critique group last week thanks to some amazing information from a very inspiring writer. I cannot begin to tell you how thankful I am for this group and how remarkable they are at picking apart a story or chapter and guiding the rebuilding process.
To be clear, this isn't my first writing group. I was a part of several workshops through both undergrad and grad school, and knew what I liked and what I didn't. My problem over the last few years has been trying to find a group of writers that wanted to publish and who were tough with their critiques. If you ever want to get better at your writing, then you need a set of people that are willing to tell you when you're holding back, writing crap, or blowing the reader away with crisp dialogue or realistic description.
This is where a critique group can be amazing, because a writing group is the equivalent of holding up a mirror to your writing. You're going to see your own errors in other members' stories, you're going to get called on it when you haven't given something your all, and your going to, as a consequence of it all, keep plot, character, voice, and other aspects of story in the forefront of your mind as you work.
If you feel like you're writing in a vacuum and don't know if your story is really coming across the way you think it is, then it might just be time to start looking for a group that will be that mirror or reality.