Beta help?

Umm...feeling my newbie status...
By this evening, I should have a draft of my 

lupin_snape Dark Side fic and I need a beta. I do not have a regular beta and have only ever used a beta once before. Eeep. Can anyone advise me on the best way to find a beta here? I saw the big list of betas, but don't know who to contact first, etc. 
The fic is about 4,000 words. Angst, violence. Hard R.
I'd really appreciate any help in overcoming my sad ignorance on the matter.

Thanks!