DO give them a properly formatted, grammatically-correct, spell-checked manuscript.* It’s annoying as hell to wade through someone’s poor grammar to try and understand their story.
DON’T respond to critiques about poor formatting, poor grammar, misspellings, or misused words with “that’s just how I like to do it.” That’s fine if you’re journalling just for yourself, but the second you give someone a manuscript to read you’re on their time and you owe it to them to follow the rules of engagement. Also, you sound like an entitled twat.**
DO include any relevant reference material. Maps (especially for alternate world settings) and glossaries are useful for understanding some stories.
DON’T foist your whole world-building bible off on them so they can be awed by your genius. They won’t be.
DO offer compensation. Some don’t want it, but you should still offer. It doesn’t have to be money. I have paid beta readers in reciprocal critiques, hugs, wine, knitted socks, and curry.
DON’T only give them what you promised if they say they loved it without reservation. Seriously, if you’re this fragile, you don’t need a beta reader; you need a therapist.
DO listen carefully to whatever they say. You don’t have to like it, but you should listen.
DON’T summarily reject or accept everything. Think about it all, and then take what’s useful. If they’re a good critic, most of what they tell you will be useful, even if you don’t want to hear it.
DO secure your baggage. Mostly, stow your fucking ego.
DON’T ask for a critique if you don’t want to hear it. Ask for something else. Some bubble wrap, maybe.
DO someone else while the beta reader is working on it. Literally anything else. Work on a new story. Write query letters. Learn ancient Arabic. Regrout the bathroom. Anything.
DON’T nag them to finish. Are annoyance and obligation really the feelings you want your story to evoke?
DO expect a reasonable time-frame for return. What constitutes ‘reasonable’ will vary according to every reader. You should talk about it when you hand over the manuscript.
DON’T expect them to drop everything else to work on it. People have lives, and they do not revolve around you.
DO treat them with respect, and thank them for their time. Really, this should be your mantra for dealing with everyone. And if it’s not, well, it’s going to take more than a writing blog to help you.
*As much as you can. Software can do weird things, but you shouldn’t do weird things on your own, and if you can’t master the rules of grammar, spelling, and proper word use, you should work on those before you go looking for beta readers.
**If that’s your ‘brand’, then please go away forever.