Review the exam structure and contents on the ADA's (American Dental Association's) website. The DAT is only offered on the computer, and it has 4 sections: natural sciences, perceptual ability, reading comprehension, and quantitative reasoning. The total duration of the test is 4 hours and 15 minutes.
The ADA website has sample tests that you can download, and all the information you need about registering and releasing your scores.
Get a DAT study guide with sample questions from real DAT examinations. Practice doing the problems quickly so that you will not run out of time on the real exam. The key to getting a high score is to do well on every section, not ace one section and get so-so scores on the others. Doing tons of DAT practice problems will help you achieve this.
Review your notes from your biology, general chemistry, and organic chemistry classes. The DAT tests you on plant and animal cell structure, biological reactions, inorganic chemical reactions, and properties of organic molecules. Physics, earth sciences, and population biology are not tested.
If you struggle with the perceptual ability subtest, make sure you get a DAT study guide with complete explanations. This will help you think like the test maker when it comes to visualizing objects.
Consider each of the 6 views for 3-d objects: top, bottom, front, back, left side, right side. Also, use your hands and your imagination to manipulate invisible objects if that helps you.
Practice reading comprehension questions in a quiet area where you can focus without distractions. DAT reading passages are fairly long and technical. They have upwards of 10 questions accompanying each passage, so it is important to concentrate. Take notes as you read to record the main ideas, points of view, and key details.
Always practice quantitative problems without a calculator. On the DAT, all arithmetic computations must be done on scratch paper or in your head. Review the rules for basic operations. Even though the problems are high school level math, they can be tricky if you forget a key concept. This is the easiest section to ace, since you have known this material the longest.
In the month before you take real exam, take several full length practice DAT exams to build up some endurance. Try to relax, and keep in mind that an average score is sufficient to get into most dental schools. But a high score never hurts!