Aeronautical knowledge includes diverse and interesting subjects like aerodynamics, how the systems of the airplane you are flying work, what weather to avoid, FAA regulations, principles of navigation, aeromedical factors, stall/spin awareness, and National Transportation Safety Board incident/accident reporting requirements. The FAA requires that you pass a knowledge test covering these subject areas with a grade of 70 percent or better.
Because the ability to "mind meld" isn't within our human capabilities yet, you'll need to study either on your own, through a ground school, or both. The good news is that the flight training industry has developed excellent books, videos, and computer training programs such as Sporty's Academy and King Schools to help you conduct your own ground school training. These courses all but guarantee you will understand and pass the knowledge test. Keep in mind that you do not need to be an aeronautical engineer or math whiz, just diligent. And with home study programs, you can work at your own pace.
What is the best way to prepare for the knowledge test? Again, this depends on the individual. If you are not motivated to study on your own, you will probably do better going to a scheduled ground school class twice a week. On the other hand, if you are self-motivated, you'll have no problem with a home-study course, along with some guidance from an instructor. What about the intensive two-day, weekend ground schools? The sole purpose of these intensive courses is to prepare you to answer the FAA test questions, so it will help you in the long run if you have reviewed the material ahead of time. There is a big difference between knowing and understanding, or as Charles Kettering, the inventor of the electric starter, said, "You can know a lot about something and not really understand it."
No matter how you decide to prepare, the best thing you can do to ensure that you understand the material is to use a variety of resources. Read aviation magazines and try different books, tapes, and videos about flying—just because a book comes in a kit from your flight school doesn't mean it's the only one you should read. Perhaps a difficult subject area can be better explained by another author. Most of all, remember that flying lessons and aeronautical study areas are related. Go prepared for each flight lesson by reading ahead so you can get the most out of your investment.
When you're ready to take the knowledge test, you will need to go to a designated testing facility where you will take the test on a computer. The flight school you attend may be set up to administer the test, or you can go to a private FAA-designated test site. CATS FAA Testing Centers offers discounts to AOPA members. Your test results will be given to you immediately, and you'll want to hold on to them because you'll need to give them to the FAA examiner when you take your practical test. Once you have taken the knowledge test, you have 24 months to complete your practical test, or you'll need to take the knowledge test again.