Wow @ Laughaholic... self-studying LANG? I was thinking of world but I have too much going on, I thought. That's pretty late dude. This is the AP test i'm worried about (bio i get fives on the practice tests, I'm not worried about that. Calc, provided I don't make dumb mistakes, I should do fine if I go over all my notes. Gov, psh. Don't even mention it. I got a 100 on the midterm. Done. Now Lang, that's polar opposite. I'm not really amazing at multiple choice, so if I don't nail the essays, I'm bound for a four, which I already have two anyways so I mean, not the worst.
My AP lang teacher is like notorious at our school for giving tough grades and whenever we have big papers, self-esteem plummets.

anyways, what she would say is like basically, don't do cookie-cutter, cliche stuff, don't do stupid things and have clear, concise, and understandable points. Also, have four paragraphs, intro, and at least a conclusion (or else your essay is deemed unfinished and you score lower than you would have if you had a sentence to cap it off.) Make the beginning half stronger than the last, first impression and that kind of thing. And read news and keep up with current events, because that's basically what the opinion essay is: You either know what the prompt is talking about, or you don't and you bomb it.
Man, you must be pretty fricking good at writing to decide to self-study this. Best of luck to you!