When I first started writing, I never realized just how many people could have very elaborate opinions about anything I created. I would offer a little poem or short story to someone to get some feedback, and their response would be longer than my piece of work. It was quite the revelation, but as I soon discovered, not a lot of it was helpful.
And of course there are the people who will offer you a very deep, engaged discussion on how they would've written it. Of course this can be informative, but the fact of the matter is that you are the writer and they should not be taking the opportunity to pour out their ideas onto your work. To those critics, I often say, "Thanks anyway."
The point I am getting at is simple: When you want some kind of feedback on a piece, it is best to start by knowing just what kind of feedback you are looking for, then seeking it. This pursuit can fall into a lot of different categories, so I will flesh out a few of the broader concepts then let you find the kind of critique you need for a piece.
(Note: a critic is different than an editor. Look at my post, The Editor Checklist, for information on that subject.)
What's wrong with my story? When we write something that just doesn't feel like it works (whatever that may be), we need to find someone who is willing to read, process, and tell you if the story thread is continuous and sensible, if the twists work, and how it fits as a whole. The critic who will tell you whether or not they like it isn't very helpful in this case because you, the writer, are feeling off about it. Maybe you are just off the mark or overly critical, but in this case you need a critic who is willing to discuss any and all shortcomings. A tough one to find indeed.
Does this story work? Have you ever written a heart-wrenching short story then wondered if it will move anyone other than you? Do you question whether your horror story will scare anyone other than yourself? This is where you simply need a gut reaction from your reader. Their critique should be as simple as, "That made me sad," "That was a creepy story," or "Meh." After that, you can have a little Q&A to dig into the details, but that point is up to you. This critic serves merely as an external opinion, which can be valuable if the writer has been looking at the same story for too long.
What's right with my story? This may sound like a weird question to ask a critic, but it can be important for us as writers. Sometimes, writing can bog us down to where we are doubting our every word, and we just need a little lift. Getting someone to read our piece and give us some positive (not constructive) feedback can be uplifting and energizing. As long as the critic understands what you are looking for ahead of time, this can be a very beneficial endeavor.
There are a few other types I will discuss later, but think about these three categories before you seek input from an outside source. Figure out which serves you best, then track them down and get a few good words from them. It will pay off in the long-run.