As a beta-reader, I feel that my job is to not just improve your story, but to improve you as an author, so that in the future, you can proceed with less help. [That said, if you just want someone to knock your plot, I can do that, too. ;-)] I will critique everything from spelling to overall mood of a story, all the way down to stylistic points, like where you put italics. A story is just as much about the visual image it projects from the page as the actual work itself. This is why mankind invented paragraphs. My style of beta-reading is to copy/paste the work I'm reading into an MSWord document, then insert comments as I go. I find that this is streamlined, and far easier to follow than going on a point-by-point basis. Very simple, that.
If you want me to beta something for you, then it will require you be willing to take some solid body blows. I'm a nice dude, but if you're doing something wrong, I will let you know. Nicely, always encouragingly, and constructively, but I'll tell you. So no easily broken noses. Or else bring a big wad of tissues.
That said, I can also treat different personalities differently. For a brass kind of person, I'll happily go mano-a-mano with you and just be straight. For a gentler person, I will likewise be gentle.
I guess what I'm getting at is that I'm pretty accessible. That said, my life is a rather exciting one for reasons that I cannot go into here, so you never know when I'll disappear for a month at a time. Never fear, though, I'll give you advance warning if I'm at all able.