I took it in June for the third time. My cumulative SAT score (taking my best scores) is as follows.
800 W (11 essay)
I have always been a reader and thus the critical reading and writing sections come naturally to me. The math, not so much! That was my hardest section. I know my math score is lame but I actually brought it up 100 points. So my score is lopsided, but eh.
Math-- use the college board SAT prep book. Maybe get a tutor, depending on your strengths and weaknesses. Study math concepts and do practice problems. Target the types of problems you can't do.
Reading-- Don't just study vocab words. Do practice tests and passages. It's easy to get burned out while doing the critical reading sections, so make sure you sit through a whole section at a time and also a whole practice test.
Writing-- Honestly I don't understand why so many people struggle with this. I got an 800 on my first try and on my third try. I think it's the easiest section. I went over a few basic grammar rules and sentence structure rules that we often overlook in spoken english, and then I was set. The writing questions are always the same. Different words, but the same mistakes that you have to correct. So I guess you should do practice tests.
For the essay, use personal examples AND literary ones. I used a literary example and gained a bonus point on my essay last time. And the people who read your essay don't know you, so feel free to make up experiences and take the easiest position you can, even if you don't agree with it. Don't go for a five paragraph essay. You need a good intro with a grabber and good grammar (the readers skim over your essays in a matter of seconds; they check for the important stuff and move on), maybe two solid body paragraphs with examples, and a final paragraph that reaches a broad conclusion with a little "nugget" (an interesting viewpoint or something you gleaned from the prompt). This will make your essay shine next to all the boring ones the judges read.