I was never entirely sure what a Beta Reader is, until I actually decided to read the description (duh). And then it seemed to me that yeah, I could do that =)
I guess I should let you know my experience, so here goes:
Fan Fiction wise, I started writing back in 2007, when I really got into Naruto and discovered all the fictions floating around the 'net. I've written three major fan fictions, which are part of a series. These were posted on another site, whilst I totally forgot about my account on here *sweat drop* whoops, you got me there!
General writing wise, I've written from a really young age, and I've always loved it. I'm a published poet (yeesh, only one poem, and it embarasses me a little), and I study Creative Writing at university. I'm in my second year, and I get good marks for my stuff! *proud*
I am into my grammar and correct spelling, but I'm always friendly about it =)
I do live in the UK, so I use the English spellings for words like 'favourite', 'honour', etc. But I'll keep in mind that you guys in the US spell them differently *cough*weirdly*cough* =P
My fan fictions on this site are all Naruto based, and that's the anime I know most about. I've put down Death Note and Twilight as preferences, mostly because they're my other two obsessions, and I know a silly amount about them.
I'm a self-confessed otaku, and I like to think I'm pretty 'down with the lingo' a lot of people like to slip into their stories, eg. 'arigato', honorofics and other romanji Japanese.