This goes to those who haven't decided yet what they are going to do in life.
It's important to start thinking about it now, no matter how old you are. You better start early because it takes time, effort and dedication to improve one's skills and to reach goals. The earlier you start, the more time you have to mess up (and you will probably mess up on the way).

To decide about what to do, there are basically 3 things you need to consider:
 - what you love, what you are passionate about.
 - what your talents are, what you are naturally good at, but the skills you acquired on the way matter too.
 - what value you can create, what you can do that people will pay you for.
Now, it's generally easy to come up with what you love most. However, I noticed that many people have issues combining that with their strengths and the value they can create. If that's also your case, you can try the following.
Let's consider your phone book. In that, you got a friend for pretty much anything. When your computer is screwed up, you know which friend to call. When you feel depressed, there is that one friend, you call to cheer you up. When you want to hang out in town, you also know whom to contact. Well, we can come up with many similar examples, but the point is, you are also a contact to your friends. So ask yourself, what is it that they contact you to help them for? That may gave you a clue of what you are good at and how you can help others.
Wishing you all the best,