Become familiar with the format of the test. Your strategy will differ if the test is on paper rather than computerized. Be sure to practice using the same medium as the one you will face on test day. Learn the length of the test and how many sections it has, as well as the subjects tested and how much you have to know on each. Review sample tests published by the test maker, reading through and memorizing the instructions to each section so you won't waste precious time on the real test doing so.
Take a diagnostic practice test, using a facsimile of the real test, in test-like conditions. Buy a test prep book, take a course or go to a test center to take a practice test. If you do the test yourself, be sure to accurately time each section and use the test maker's bubble sheets for your answers. Take the test in one sitting if that is how it will be administered when you take it for real. Once you have your results, review and bone up on your weak areas.
Use a process of elimination on multiple-choice questions, covering up the answers first. Especially with reading and verbal questions, it is to your advantage to cover the answers and come up with your own answer first. Bring a big flat eraser to the test and use it to physically cover those answers. Think of your own word and jot it down on the test booklet; it's then safe to uncover the answers. Cross off the letter of each answer that is inconsistent with your word until you find the correct answer.
Don't sweat it; squiggle it. If you don't know the meaning of a word, resist the impulse to reject it, since it could be the correct answer. Instead, put a squiggle in front of the letter of the answer and try all the other answers first. It may turn out that the other answers are wrong, so you can choose that word, after all, or you may find the answer easily among the other choices, which allows you to save time wondering about the mystery word.
Slow down and get more easy answers right. Many test takers will rush through the easy questions, getting a few wrong in their haste, and then get stuck on the harder ones, where more time won't necessarily help them find the answers anyway. Don't make that mistake. If the test scores every answer equally, use your time to rack up as many easy points as you can.
If the test has an error penalty, it is sometimes to your advantage to guess. The SAT, for example, takes one point off for every four errors per section. On that test, students should guess if they can eliminate at least one of the five answer choices for a question. On the ACT, however, there is no error penalty, so students must make sure that no answers are left blank. If time is short, just fill every remaining answer on the bubble sheet with the same letter, going straight down. (This also helps you analyze your results, as you will recognize that letter as the one you chose for those questions that you didn't have time to do.)
Test tricks help you leverage partial knowledge, optimize your test-taking time and avoid typical errors. The best way to increase your score, however, is through thorough and pin-pointed study, practice tests and review of your mistakes. Plan a long-term schedule that allows you to take the test more than once, if possible, so that you may have a chance to raise your score.