Well, I'm in pilot training right now madddog, so I'll tell you how I got here and you can draw your own conclusions on what you need to do with your own life.
Step 1, if you're a junior in high school and haven't started seriously thinking about where you want to go to college, you're behind. And even though it's a painful four years, don't count out a service academy. The Air Force Academy gets as many pilot slots every year as all of ROTC combined, so almost everyone who is medically qualified at graduation gets a slot. No matter which route you take, you have to be an officer to fly a military jet, and that means you need a Bachelor's degree. Start looking at the application process, Academy or ROTC, ASAP. You might be surprised how much you have to get done. Waiting until senior year will be waiting until it's too late. SAT/ACT scores are a big factor, but not the only factor.
I hate to be the one to say it, but math is probably the most important subject for you to do well in. You can major in anything you want to, the military doesn't care what your degree is in. But if you want to fly, there is a lot of math involved in figuring out how long you can stay airborn, how much gas you have, where the center of gravity is on your plane, how it will change when you drop a load of bombs, etc.
What it boils down to, I guess, is that you're not going to be able to just walk into a pilot slot. There's always a line of guys waiting to get it, and you have to push yourself a little harder to stay near the top of a very long list. If you're willing to put in the effort though, the military will put the time and money into training you to do one of the coolest jobs in the world.
Now that the lecture is out of the way, here's how the pilot training process works. First, you get a Bachelor's degree and get commissioned. Then you'll go through Introductory Flight Training (IFT). IFT consists of getting your private pilot's license in a Cessna 172 or something similar. That's the screening program. From there you'll go to Undergraduate Pilot Training (UPT). By the time you start, I'm sure the T-37s will be all phased out, so you'll start flying in the new T-6 Texan II's. After about 6 months of training in the T-6, you'll want to get into the T-38 track. The T-1 track is for people going on to fly tanker/transport aircraft, the T-38s are for people going to fighters/bombers. You'll spend another six months in T-38s. At the end of that time, you'll graduate from UPT and get your wings. You'll also get your assignment for which plane you'll make a career of flying. Before you get there though, you'll go to Introduction to Fighter Fundamentals (IFF). I'm not sure how long IFF is, but I think it's only about 3 or 4 months. That's where you'll learn a lot of how we fly fighters in combat. After that, you're off to learn how to fly your F-15 or F-16 or whatever it is you want.
Of course, this is all based on you joining the Air Force. Obviously, there are some differences if you want to fly for the Navy or Marines. Sorry I can't tell you more about life in those branches, I only know the way I'm doing it.
This was a really long answer to say that you need to get started early and keep working hard all the way through, but there you have it. Best of luck, I look forward to serving with you some day.