The most common tests students take when applying for grad school are the Graduate Management Admission Test (GMAT - for business school), Law School Admission Test (LSAT), Graduate Record Examination (GRE), and Medical College Admission Test (MCAT). Scores are generally valid for five years. If you are considering applying for a graduate degree in the near future, you may want to consider taking the standardized test in your senior year. You should take summer or early fall tests if you plan to apply to graduate school in the upcoming year.
The following websites will provide you with specific information on test dates and content of testing materials.