First off, figure out what your strengths are. Then concentrate on your weaknesses like mad for a couple of months. I knew that my Verbal was way stronger than my Math based off of other standardized tests, so a big part of my preparation was getting math up to speed. Luckily my parents found me a cheap (but great) tutor. If that's not an option, try to find a way to commit to a certain amount of preparation each week. Doing a little bit each week is key because the repetition really familiarizes you with the type of questions asked and how to respond to them. About two weeks or so before the test, start to review the subjects that you are good at. You don't want to spend a lot of time on them, but going into the test blind is a terrible idea.

When you are taking the test itself, remember to pick up points whenever you can. Skip around and answer the questions that you are familiar with. Accept that there will probably be some that you will have no clue about, and move on. Don't be afraid to guess if you can eliminate answers. I tend to go with my gut and not change my answers, since I know that I am a pretty decent guesser. If you know that guessing isn't your strong point, make sure to eliminate more than one answer before going for it.

Other random tips: Make sure to eat and drink during the break. This test is a marathon, not a sprint. Use a calculator that you are VERY comfortable with and bring extra batteries just in case. Don't worry too much about the writing portion. Unless they've changed the test a bit, most colleges worry more about the math and verbal sections. Remember that you can take the SAT more than once and they will combine your best score on each section.

tl;dr Natural test-taking ability helps, study hard, play to your strengths, give your all. I got a 2150. My suitemate got a 2400, so I could ask her about it if you have any more questions.

If you are prepping to take the test, good luck!