Every year, the SAT gets a few minor tweaks. Every year, Ed Carroll retakes it, and retakes it, and retakes it again to find those tweaks.

Carroll is the executive director of high school programs for the Princeton Review, which makes him responsible for the study guides that high school students around the country are, right this moment, using to cram. On Saturday, this year’s students will take the SAT for the first time in 2009.

Carroll knows as much as anybody what obstacles students will face. We talked to him about the SAT and the other main exam for college applicants, the ACT.

Q. You’ve taken every SAT for the past 10 years?

A. I’ve taken every test that the College Board releases. They release at least three a year and I take all of those. I’ve taken it live a bunch of times – I sit with a bunch of high school students. It is a skill that can be learned. Excellence on this test is something that can be learned through practice, very much like learning to play the piano or tennis or cooking.

Q. How different is it from year to year?

A. It is absolutely something that is consistent, because it is a standardized test. You don’t know exactly what the vocabulary will be or what the math questions are, but you know the scope of what the math will be. From our perspective, from an analytic research perspective, they change very little.

What I’m looking for is to see what the test is doing. So, like, essays, I’ll write it with one example to support my point, then on another with two examples, then one with three. Or use personal examples on one, versus historical on another. Or with misspellings. I’m trying to see what the test is doing.

Q. So what is the test doing?

A. The mechanics of writing – spelling, punctuation and vocab – that most people think matter, on the SAT they matter less. I never say they don’t matter – but they don’t matter really. The biggest impact on your score that will most influence good scores: Answer the question clearly, arguing it strongly pro and con. And have support, examples from literature or current events or maybe even personal examples. And have some sort of organizational structure, a conclusion that mimics your introduction to demonstrate you stayed on topic the whole time. Those things that make a good creative writer really don’t matter on a test.

Q. Should students keep taking the test over and over in practice and real life?

A. Scores tend to plateau by three tests. So I usually discourage that.

Q . What sorts of students are better served taking the ACT instead of the SAT?

A. ACT doesn’t directly test vocabulary, SAT does. If you’re a decent reader without a decent vocabulary, the ACT is better for you. In math, the ACT will test basic trigonometry and imaginary numbers. The content in the ACT math is harder.

The SAT is known for having questions that are more deceptive. The ACT is not known to have quite so many that would be called deceptively tricky. And 10 times in the SAT you’re going to have someone say times up, put your pencil down. There is more of a pressure element to the SAT because of that.

Q. What’s a worst-case scenario for someone taking the SAT? What could go horribly wrong?

A. I know too many high school students who think it’s a good idea for the first time in their lives to start drinking coffee the first day of the test. That’s very, very, very, very dumb –I don’t know how else to say that. And there is no good reason not to write down your answers in the booklet and circle them in the page; everybody thinks it won’t happen to them and then they’re on No. 10 on the answer sheet but No. 11 in the book. Bring a snack. The SAT is a test of endurance.

Q. What common myths about the SAT are wrong?

A. There is no better time of year to take it – people think you have an advantage if you take it at a certain time of year. It’s a standardized test, so they’re all pretty similar and there’s no way to predict it.

The classic myth is some people think if you don’t know what to do, guess C. No. C shows up once out of five times. They’re very good about designing these tests. We find unintended patterns. When we find them, we expose them.