There are 2 ways to determine what you want to do in life:

1) You’ve seen someone’s career and really want to do what they do. E.g. If your dad’s a lawyer, and you want to be a lawyer like him, or your aunt’s a school teacher and you think she seems to be having lots of fun in her job, or your cousin’s a reporter, and you like the exciting life he leads.

2) You’re good in certain subjects, have certain strengths and talents in yourself already, that would make it easier for you to be successful in certain fields. E.g. You’ve been active in the red cross and so you’ve already learned something about taking care of injured people, you find you like it and want to continue doing that as your career.

So, the first thing to do is some research. How could you decide that you like something if you don’t know what it is exactly?

a) What does your family do? Find out about the careers of your parents, uncles / aunts, neighbors, friends’ parents, etc etc etc. You won’t have a great many careers there perhaps, but you’d know firsthand about certain jobs.

b) What careers can you see on tv and in the movies? (doctors, lawyers, business people, fashion designers, private investigators, news announcers, reporters, artists) These portrayals may not be entirely accurate, but they can give you an indication of some of the things involved in each career. You’ll have to do some online research.

c) What other careers are there? There are sites that list people’s occupations, and even some career guidance sites where typical careers are listed. What have you missed from the list you’ve made in (a) and (b)? Google these careers. Find out about what people do in those careers.

Then we go to the next stage. Ask yourself:

What do you do best? What subjects?
Are you a physical person, meaning do you like to be active and going here, there everywhere, or do you prefer sitting in one place?
Are you athletic?
Do you like to read?
Do you like working with your hands?
Do you like being by yourself, doing things alone or do you prefer working together in a team?
What do you like to watch on tv? Do you prefer action movies, discovery channel, Oprah?

These questions and many others allow us to understand ourselves.

from the list of possible careers, find what is the most interesting ones, based on the things that you need to DO once you’re in the job. NOT based on what other people will think of you, the money you’ll make or any other stuff. Ask yourself

WHICH JOB WOULD ALLOW YOU TO DO THE THINGS YOU ENJOY THE MOST?
WHICH JOB WOULD ALLOW YOU TO TAKE ADVANTAGE OF YOUR NATURAL TALENTS?

Once you’ve answered these questions, you might not have only one career option. Its good if you make this a rather long list. Because there’s another stage:

Once you’ve shortlisted the likely careers, you need to find out what you need to do in order to take that career choice, and what are the things you can do to give yourself a headstart in it. In some careers you need to get a degree. If you can go to a reputable university, then you’d have more of a head start in that career. In some careers, you need to work with certain well-known people who are already in the industry. In other careers still, talent is what matters, not education or connections.

Once you know all this, then you can decide. You can’t decide in a vacuum. Most young people have not much idea about careers because they’ve not worked before, and even if they had, these are odd-jobs or manual labor that they don’t want to choose as their ultimate career. Don’t get impatient. Get info methodically and systematically. You should put in the effort now. People have gone into depression, committed suicide, became abusive / alcoholics, became homeless… all because they chose the wrong career and don’t know how to get out of it. So, do your research. YOu know yourself best. Think about what would give you joy and contentment in the long run. Like, visualize yourself doing this thing for the next 20 years. Can you see yourself doing that? If you can, then thats probably a good career to choose.
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