Know what your math test scores are from previous standardized tests. Talk to your guidance counselor as well as your math and science teachers to find out what areas you need help with. They can also tell you what math concepts you have mastered.
Find a mentor or coach to help you study for the OGT. This person should be someone who knows a lot about math and who has the time to help you. You should also trust this person. Since you are asking your mentor to give you some of her time, it is important that you be responsible about your end of the commitment.
Share your scores with your mentor. With your mentor's help, learn how to mind-map problems. Studies show that students who not only read and understand problems but also understand how their minds solve the problems do better on tests. Mind-mapping helps you learn how you think.
Take OGT practice tests that are available. These aren't the actual test questions, but they do give you a good idea of the concepts that are on the OGT math section. Use your mind-mapping skills to do your best. Go over the results with your mentor. Continue to work on problem areas until you master them.
Eat a good breakfast on the day of the test. Go into the test with a good attitude. You not only have the skills necessary to pass the math section but also do well on it.