One question I'm often asked about SAT I Math test results is: "Why did my son/daughter miss so many easy questions and get the majority of hard questions right?" For me, this was the most difficult obstacle to overcome when it came to peak performance on test day. After drilling countless practice problems and tests, it is a natural inclination to race through the first "easy" math questions and spend more time on the "hard" ones. The blame is often assigned to "careless errors"--as if students didn't care enough to go back and check the answers. Sometimes dyslexia or ADD/ADHD is blamed. In reality, the test makers are teaching students an important lesson on pacing and discipline.
Initially, I had thought that the key to the best scores was pattern recognition. That is, work enough problems, and you'll have seen it all. This actually isn't so far from the truth; however, the devil lies in the details. The problems I was getting wrong the most often were the ones that looked exactly like a mundane Algebra or Triangles question-- usually one I could do in my head. What would trip me up was that, by thinking "Hey, this is cake", and rushing through, I would often answer the question I assumed was being asked instead of what was actually being asked. For brain farts like that, the test makers provide some wrong "teaser" answers to make students think they're on the right track. Be especially wary of problems that you think you can "solve in your head".
To get to the 700-800 range, a student must have the mentality that each question is as vital as the next-- something like a Zen mindset (meditation really does help before exams!). I don't mean to say that students should devote an equal amount of time to each question, but that, in terms of the big gizmo that scans your answer bubblesheet, it doesn't care if you got number 3 or number 17 wrong: the point penalty is the same. So, always physically annotate (underline, circle, star, etc.) what the question is asking in your booklet. Working steadily and calmly is the best approach, and I work extensively with students on timing issues.