When I betaread, I do a lot of editing. I'm warning you now, if you don't want someone being picky with your writing, you shouldn't ask me to do this for you. I pick stories apart, but you have to remember that I'm only doing it to make you a better writer. The more I like something/the better it is, the more I'll edit it. It makes sense, in a backwards sort of way.
When betareading, I read through and make note of any grammar/spelling errors. I'll also look for things that get in the way of the story: repetitions, cliche usage, very long sentences, etc.

As I already mentioned, I'm a grammar Nazi. I have good spelling and grammar, and I'm pretty good at looking for flow and things that make the story unclear.

I sometimes overedit pieces a bit. Also, I somewhat lazy sometimes, though I'll do my best to get your story back to you when you need it. If I don't like something, I'll show it.

I prefer to read stories with an at least somewhat original plot and good writing. My favorites tend to be angsty stories, anything thought-provoking, and/or things that are a bit outside the norm. I adore odd ships and slash is fine with me. I don't mind reading things that are a bit more adult.
Length of the story doesn't matter.
I also prefer stories using mostly canon characters, though I have found some good ones that are mainly OCs.

I would rather not read anything that's pure smut. If it's fluff, you have to read it well. If it's clogged up with too many OCs, I sometimes find that annoying. Especially if you've written a Sue.

All Books

Romance Humor

Poetry Angst

Supernatural Sci-Fi

Fantasy