Not an expert. Not saying this is what beta readers should be or do or say. This is not a list of commands for all beta readers everywhere and I'm not commenting on whether this is the best way for other writers to go about getting feedback.
I just know what works for me and my personality. I have thin skin. But I want reactions. Sure, I'll take a positive stroke over a negative one, who wouldn't? But overall, I want a little help as I know I can't be totally objective about my little baby.
So what I really want when I ask someone to beta read one of my stories is for them to answer this question: Does the story work?
What do I mean? My goal is to entertain readers. I want someone to be drawn in and enjoy the story. As my son-in-law says, "You play games, you listen to music, you look at art, you read books, and you watch movies. But you experience stories." It's the story, first and foremost, that I'm after.
That said, here's a quick list of dos and don'ts for potential beta readers.
What I'm Not Looking For: Someone who...
...wants to rewrite my story and tell it the way they would tell it.
...wants to nitpick over word choice and sentence structure.
...has to obey those squiggly lines in a Word document.
...doesn't like my story and storytelling style.
What I Am Looking For: Someone who...
...tells me when something doesn't quite work for them.
...suggests how a scene might work differently.
...finds plot holes and dangling details.
...doesn't worry if I ignore their advice.
...teases out awkward sentences and dialog.
...catches typos, grammar goofs, wrong words.
...tells me what parts they really enjoy and why.
...likes me, likes my voice, and likes my stories.
I don't edit edit edit. I'm not going to set my manuscript aside for a few months and come back and rearrange scenes and cut out extraneous material. I edit as I go, get feedback as I go, and fix mistakes as I go. It's basically a 3-draft process: Write, Fix, Polish.
Oh, and then publish. Let others decide if they like it or not. If it sells, I've struck a chord. If not, then at least I've had 4 or 5 beta readers enjoy the storytelling process with me and are open to my next project.
This is me. Again, not an expert. Not saying other writers (newish, like me) should do the same. But for those interested in this approach, here's a link to an article which I've found helpful in developing my philosophy. Your approach will be different. In the future, mine may be as well. For now, write on.