Preliminary scholastic assessment is a standardized test that determines the eligibility of student for the National Merit scholarship. The three disciplines in which students are assessed in PSAT exams are math, writing and critical reading skills. The major difference between SAT exams and PSAT exams are that with SAT exams your eligibility for admission in a college or universities for higher studies are determined while through PSAT exams it is only determines if you are eligible for the merit scholarship or not. Clearing any type of competitive exams whether it is PSAT exams, SAT exam, LSAT exam or any other, you need to prepare really well. So the best thing that you can do for this is to be prepared for the exams well in advance.