Inspired by a post by mmorpgsforlife. When you think of a beta, what do you think of? Copy editing has its place, but what the writing world (and most writers need/crave) are good editors. We call them good betas, here in the world of fanfiction.
There will always be a need for helpful editors. I could always use another person in my beta pool, but to be honest I don't need copy editing from my betas. I don't use spellcheck etc either--that's the the absolute basics of writing. Think Zaizen. It's rare that my betas will have to say, "That dangling modifier doesn't belong," or "You should use 'their' instead of 'they're'." I have all that, and I don't want to waste my betas' time with trivial matters like spelling errors. They do happen, but that's not what I have betas for.
What I do ask of my betas is honest negative criticism. "X doesn't work because Y or Z." "You said A earlier, and now B and C, but if you do that then D happens which throws a spanner into the works." "Ai, this is wangst." "That sounds/feels/is OOC." "Was that character cut out from cardboard?" "This concept is totally unclear." "I don't know ... something here doesn't work, but I can't put my finger on why." "Been there, done that, you can do so much better."
I have concept betas who discuss the meta and argue with me over world details and plausibility, who take a look at a general idea and go "Ew" or "Write it!", or ask me more questions when I'm being vague. Some of my concept betas are basically the bunny assassins, who read my bunny-bits on ann_applecore and veto the horrible ones or the stupid ones. We won't mention that monstrosity involving an American ex-president. Some of them go further by discussing the bunnies with me and adding their ideas/comments/suggestions, or by being a sounding board and asking the right questions ("Why did the war start?"). Some just act as enablers and feed their favorite bunnies with lots of carrots, as was the case with Dragons of the Rising Sun. ^_^;
Then, I have narrative betas who read the story once a first draft is written. They tell me when X character has moved into OOC territory or if something about a character is off ("That's far too wordy for Sanada! Ew!"). They also tell me if it's boring, if the pacing is wonky, if I have succumbed to the horrible Infodump Syndrome, if it's Just Not Working. Most of the time when the story gets to the narrative beta stage, I already have a specific problem and/or questions lined up for them. "I don't like the feel of this scene, but I can't figure out why. Help!" "Read this and tell me what the atmosphere you're picking up is like?" "I've gone over this one ten times now, but Yukimura still feels a little off to me, and I'm ready to consign him to the depths of hell!"
Some of my betas are stage-specific, and some of them do whatever I ask (and then some--most notably supporting and propping me up when I'm ready to give up *hearts you all*). All my betas have insights that differ from my own. It's great when I get people who reassure me that X or Y looks great. It's even better when after a bit (or a lot) of argument both me and my beta(s) read through what has emerged from the fire and say, "Perfect!"
Considering how much involvement I ask of my betas, I do my best to spread out the load and not bother the same people too much, though it sometimes happens that way. And yes, if I beta your work, depending on what stage you're in, that is what you get. The ideal process is a conversation between my betas and myself, where I write until we're all satisfied. If there are fundamental differences in how the writer and beta(s) view characters, though, it's unlikely a successful beta-ing arrangement can be set up, because when one disagrees on characterization, there are so many side-disagreements that stem from the disconnect that there is no point going on.
Finally, after all that, readers (final betas who aren't really betas but at the same time still are) comment and tell me what worked for them and what didn't. And that gets picked up and put into my mind for the next round.
^_^;;; Wow. That was long. Sorry Sparky, that was a bit of TL;DR. But when one sees the opportunity to tell things from this side of the fence, it's so very hard to resist that soapbox ...
ETA: I have to hasten to say that this is only true for me! O_o I don't know how other writers do this. I know one writer I beta for, ontogenesis, has a slightly different process from me. She thinks a lot more about her plot and characters before she even comes to me, and sometimes she just shows up with a few thousand words and goes, "Okay, your turn." However, I'm a very conversational type of writer. I don't write in isolation. I've tried it, and I can't--I fail horribly when that happens. Like I said, this is my point of view from my side of the fence. ^_^ That's all.
Also, I have to emphasize that not all my fics get this treatment. ^_^;;; For example, Tohoku was very much a mostly-narrative-beta sort of fic. Caramel took a LOT of concept-beta-ing, but minimal narrative-beta. His Grandfather's Dragon was very much a mash that needed a lot of narrative work and scrutiny, but Promise was so short nothing much was changed after the first draft hammered out. (There was another one for the Dragons AU that came out to a draft of 1000+ words. It did not survive beta and died.)