Beta Reading Guidelines
What Is Beta Reading?
Beta reading has been described as the critical read of a manuscript prior to publication. The beta reader reviews a manuscript for all or selected elements such as plot development, character descriptions and motivations, general readability, and inconsistencies in logic. Beta reading comes before the formal editing, and is a way of helping me to see things from your perspective as a reader. No special skills are required. If you're a keen reader of the genre, that's enough.

Typical Beta Reading
What the Beta Reader Should Do.
Read the manuscript at least twice.
First, read as a reader, not a beta reader. This is very important! You should note general feelings or problems with the manuscript, but don't let it distract you from the story.
For example, does the opening scene leave you struggling to figure out who and where the characters are? Are too many characters presented in the first chapter? Your questions might be answered as you read more, but note your feeling as you go.
With the second and later reads, focus on the areas I've asked you to check. If I'm worried that characters are flat, see if he/she is adequately developed. If you think they are not, be specific as to why they're lifeless. Are they too perfect? Are they risking nothing by their actions? Is the antagonist too evil and gives everything away?
If you notice a problem I didn't ask you to address, do point it out, tactfully and diplomatically. Do tell me when you think a scene is good or a character resonates with you, otherwise, I can easily think my work is rubbish.
So, did a character make a joke and you thought it was funny? Say so!
Did a scene make you tear up in empathy with the characters?
Were you glad when someone got killed off?
Let me know these things. It's very helpful to let me know your emotional responses to a character or scene, but don't confuse this with your personal views on the subject, or your personal preferences for writing style or content. You aren't writing the book 🙂
As a writer, I want to know what emotional response the reader had, and if it matched my intentions. Did a character's action leave you angry? Let me know. If that's the desired reaction, I'll know I got it right. But if I wanted you to feel sorry for him, I need to think about word choices—and consider the possibility that you simply misunderstood the scene. That happens.
It's okay to make a few personal observations, such as your experiences with something in the book. But don't form your critique around them, and do let me know these are "personal asides."
Be specific with comments so I clearly understand what you mean. "This character annoys me." doesn't give me much to go on. Tell me why he/she bores you. It'll help me fix the problems. Something like this is more helpful. — "Maggie doesn't seem to have any morals. She never has a good thought about anyone. I don't know why anyone would hang out with her, never mind help her."
If a passage confuses you, explain why. — "Frank has helped Maggie throughout the first 21 chapters. There was no good reason for her to abandon him when he passed out after drinking too much, and yet she did. Why? If there's a reason, the reader needs to know it. If there isn't one, you might want to reconsider her reactions."
Be tactful and diplomatic with your comments and recommendations for rewrite/revision. This is an area where you should be honest, but not unkind. Phrase your comments as suggestions rather than instructions or complaints. Comments like, "you keep dumping too much backstory at the beginning of every chapter" may be accurate, but take a softer tone. For example, "Readers might skim over the first part of your chapters to get to the action. You might want to rework some of the backstory elements into a character's internal thoughts or a dialogue exchange and spread them through the story."
Wait a day or two after writing your comments before you send them. Then re-read them. How would you feel if you received the comments phrased as they are? Could they be more tactful? Are they clear? Have you pointed out areas that are working well? Is it balanced?
What the Beta Reader Should Not Do.
Never make insensitive or inflammatory comments. Beta reading and critiques should never be personal judgement of the work or the writer. Don't limit your comments to those of the "Here's what needs work" category. Begin and end your comments with things you enjoyed. Don't take it personally if I don't incorporate all of your suggestions. Maybe five other people loved something you hated. I have to make the final call on what works.
And there you have the basics of beta reading. I hope this has helped you understand the process and see how such a critique should work. It can help you make my work the best it can be.