1. And this is the most important one...Does it sound right? Do you get it? Does it make you feel that the doors to Paradise have suddenly swung open and you can now see the light? Yes? Then grab the feedback with both hands and implement it.
2. Sometimes feedback is right, but the solution is wrong. People like being helpful, so they like giving a solution alongside what they see as the problem. Sometimes they can't articulate the problem, they just know they have a solution for it.
For example, the feedback might go along the lines of: "You could make your main character take a job at the local supermarket." That's a solution. The problem is something like, "The main character is a bit wishy washy and I find it really irritating that they sit back and expect other people to sort out their financial problems for them - they need to take some action that shows they are at least trying to support themselves financially."
That sort of feedback is golden: now you can work out what the action that they're going to take will be.
3. Feedback is all about how a reader perceives the character and the situation. This will almost certainly be coloured by their own experiences. However, if several readers are pointing out the same issues, then you can be fairly certain that's a true response. Act accordingly.
4. Sometimes you're too close to see it. Writers spend a lot of time in their heads. We might appear to be going for a walk, driving the car, or doing the washing up but really we're busy writing stories in our head. These stories are always brilliant - I'm frequently walking around with tears rolling down my face as the tragedy in my head unfolds, or laughing inappropriately because one of my characters has just done something incredibly funny.
The trouble is what works in our heads doesn't always translate to the page. When we look at the page, we might see what we wrote in our head, not what we've actually written. A reader can only read what's on the page, and not what's in your head. A sure sign of this is when you find yourself explaining what's going on to a puzzled reader and how they have missed the point. Stop! It's your job to write clearly enough so they don't miss the point.
5. If we're honest with ourselves, we sometimes have little niggles about the work that we hope will magically go away if we don't think about them. Perhaps, we hope, perhaps no one else can see that glitch in the story. Feedback can good for confirming that those glitches do exist and somehow we've got to deal with them. Sigh. I wish it wasn't like that and the glitches would magically disappear by ignoring them but there it is. They don't.