Let's face it, you are going to spend a large part of your life working. Why not find something you love to do? Chances are, you'll be happier and more successful at your job - no matter what your chosen occupation is. One of the best ways to figure out the careers you would like to research further is to first research yourself. Ask yourself, what is it that you love to do?
Right now, you most likely spend the majority of your time at school. Your favorite part about school might be seeing your friends, but what about your favorite courses? Make a list of those, and look at them closely. What is it about those classes you like most? What do they have in common? Is it a common subject area?
You can also look at your schoolwork in terms of the type of work you were required to do for the course. If you enjoyed solving algebra problems more than writing a paper about Shakespeare, that's important. Maybe this is a clue that you might be better suited for jobs where problem-solving is a daily task.
Looking at what you prefer in general is beneficial, too. If you like to be around others most of the time, a job where you come into contact with people on a regular basis might be more satisfying. While this doesn't narrow down your choices a lot, it will rule out several occupations where you work alone. If you like to investigate and come up with new ways of doing things, you might consider jobs that involve computers or research (or both). If you are a hobbyist who likes to work with tools and your hands, you may have an aptitude for several careers in the skilled trades, where your work is visible and tangible.
Finally, remember that what you are good at and what you like to do are two separate things. This can mean that even if you excel at your science courses, you still might enjoy teaching kindergarten more than working in a laboratory.