well it all depends on what kind of person you are and what kinds of stuff you like. I have a friend that came back from the Marines. I met him in my math class. He likes to do math and he is good at it. He's doing business administration because you have to learn about accounting, finance, marketing and all that technical stuff. If you're more into numbers you can go into business or accounting.
If you like math and science then you should consider engineering or computer science. They make good money!
If you like biology and chemistry and you like helping people you should look into the medical field.
All these fields have great benefits but of course you will have to learn a lot! take a few years at a community college or a university and take some of these classes. Soon you will find what you like to do.
good luck!