Treat these people like royalty. They are worth their weight in gold. Who are they? Beta Readers are, at best, a mix of people. Parents and lovers are going to read your masterpiece and say you are brilliant. In their eyes you are.
But an agent hasn't fallen for you yet, so let's get some real input and prepare to go through the ms again when they are through.
My beta readers are diehard readers who respect me enough to tell me where my story doesn't work. Some of them are writers and some are not. Most of them (as it turns out) don't read literary fiction. But usually it is good to get some beta readers who read in your genre.
Care of beta readers: First off, it takes much longer to beta read an ms than a printed book. For one thing, they are looking for things for you rather than laying back and reading for enjoyment. So never, ever be argumentative to a beta reader.
It is fine to disagree, but consider if they missed the point of what you wrote, then likely you didn't write what you meant. Encourage them to tell you the hard stuff, the stuff they fear might hurt your feelings. This isn't personal. The point is to make the ms the best it can be.
I have found when a beta reader questions a sentence or word that the problem is a bigger problem than they realize. Sometimes it needs to be rewritten, moved, or deleted. So look bigger than they point out. I like to engage in a dialogue with my beta readers when they have a question and draw out as much comment and opinion as I can. They can only get a first impression the first reading, so make it count.
Some of my beta readers have been with me for ten years. We're like family. I trust them not to sugar coat things. They trust me to respect their opinion, even if I disagree.
Always be courteous. I know, that shouldn't have to be said, but when I've beta read, sometimes the writer forgets that I could have been doing something else, like my own writing rather than reading for them. I always give them a gift, a signed copy of the published book.
Sometimes I have several sets of readers. The first group goes through, I make changes, then the next group goes through. Regardless of how many or few groups of beta readers I have, there are a couple of people who I save for last because they are the gatekeepers. Nothing gets past them, nothing. Wear thick skin with these types, but they are priceless.
I don't give my beta readers strict instructions because I don't want to limit the feedback to a set number of items. I want every thought. I usually ask for them to point out things that seem amiss and things they really like (or I might change them if I don't know that is a good part - it all looks bad after a while, know what I mean?).
Some of my readers prefer paper copies and some digital mss. I accommodate them. I rather have them read on paper because it is easier for me to mark their notes, not that I incorporate all of them. Others send me a list with page and line number and change or comment. Basically, I go with the flow because the input is so valuable.
Then go back to your ms (also called WIP - work in progress) and fix the places you agree with the beta readers need fixing. By this point, I'm totally sick of the story, the characters, the title, and so ready to start something new that I could delete half of it. Then at some point, it is all okay again and I'm happy with it. I usually read through it aloud one more time. That might be a bit much, but things get missed with all that editing and rewriting and deleting.
From here, most of you will polish your synopsis and query letter. I do other stuff because I'm happy with what I'm doing with my books now and I wasn't happy before. But that's me. You have to figure out what is best for you.
Whew, I've told you all I know. Guess I'm done with this blog unless I come up with something else to write. Oh wait, the short story contest is still going on. Guess I can't quit here.