Becoming a fighter pilot isn't something that happens overnight. It requires lots of time, dedication and perseverance if you want to be successful. A special type of person is required to join such an elite group. Funnily enough, most people think that becoming a fighter pilot is mostly about flying, when in fact that isn't the case. You also need to successfully train as an officer. So you're primarily an officer, even if you continue on to be a fighter pilot. Your primary job is to defend the USA against its enemies, and any career aspirations are secondary to that.
There are three possible ways to train as an officer - service academy, Officer Candidate School (OCS) or Reserve Officers Training Corps (ROTC). As a high school student, you should apply to a service academy if you want to become an officer. You can choose between the Air Force Academy, Annapolis (Navy & Marines), West Point (Army) or the U.S. Coast Guard Academy. All of them put you through rigorous military training, and you also obtain a Bachelor of Science degree. If you have a strong aptitude to advanced math and science then you'll have a much better chance of succeeding.
If you're planning to enter one of the academies, then be aware that the competition to get in is fierce. You'll need a high school grade point average of 3.8 as a cadet, as well as a SAT score of 1300. This has to include a minimum of 1050 for verbal and math. It's a good idea to have a strong extra-curricular activity record as well, even more so if those activities demonstrate leadership or athletic skills.
So if you want to enter a service academy, earn a commission and receive a college education, the path is simple. It's not easy though - you'll need to perform very well in high school, and not just inside the classroom. It takes a long time to work your way through the application process. You certainly don't just hand over a simple form and expect to be accepted into a service academy. You need three letters of recommendation, extensive paperwork, and even to be nominated by your Congressman. To improve your chances of success, start preparing your application early, and certainly don't start any later than your junior year.
The bad news is that just because you made it into the service academy, pilot training slots are still extremely limited. Being accepted by the academy is a piece of cake by comparison. However pilots are in demand right now, as all the military streams are struggling to retain the pilots they have. So if you're keen to be a fighter pilot, it's a little easier than usual to obtain a slot. How long that lasts, nobody knows.
You might also find that The Reserve Officers Training Corps is the best option for you. With this, you study at a college or university as normal, but add in the officer training requirements. On top of your regular studies you will have to attend military training and courses, spend at least one summer on a training camp and attend weekly meetings. Most of the time you live as a civilian, only donning your military garb when you're actually attending military classes. When your officer training is complete, you can then apply for specific programs such as pilot training. Competition is tough, and you'll need to pass some rigorous academic, medical and testing requirements to be successful.
For those who decide a little later in life to become a fighter pilot, The Officer Candidate School (OCS), sometimes called The Officer Training School (OTS), is the best route. Within 4 months OCS will take a college graduate with no background in the military and turn him into an officer. Again, you have the opportunity to apply for pilot training school when you qualify as an officer, but the competition is just as fierce. It's also necessary for you to begin training as a fighter pilot before you turn 27, so this third option is only available for a limited time.