First, what test are you going to take? SAT or ACT? All colleges will accept either test for admissions. Try a practice test of each to see which one you do better on and which one you feel more comfortable with.
Second, once you have determined which test you will focus on, then it is time to take some practice tests. Get the official test book for the SAT (The Official SAT Study Guide, 2nd Ed) or the official book for the ACT (The Real ACT Prep Guide). Take practice tests to get used to the types of questions being asked.
Three, determine when you will take the actual tests. I generally recommend that students take whichever test twice during the late winter and spring of junior year. All testing should be completed by June of junior year. This can take some planning, particularly if you are taking the SAT and SAT subject tests because you can not take subject tests and the regular SAT on the same date. This is where early planning really pays off.
Four, register for the test dates early so you don’t run into problems such as having your local test center be completely booked.
There you go. Four quick steps to testing success.