Like many kids, I did want to be an astronaut, but did not understand all that went in to becoming one. Becoming a fighter pilot is one thing you can do to raise your chances. But I think the bare minimum is to have a master's degree in something like aeronautical engineering, but you are going to be a more serious contender with a doctorate and specializing in mission specific education. Maybe robotics or biology. Even as a shuttle pilot, you have many more duties to attend to in space so one cannot just become a fighter jock with a regular degree in basket weaving and expect to make it into the astronaut corps, your entire career path must be completely focused on the needs of the space program. Civic involvement is a must as well, they have to see a driven individual who can handle a great deal of stress and someone who contributes to the community where ever he may be. This isn't completely gospel, I have no doubt that the NASA website can lead you in the right direction.