How do you know what you want to do as a career?

What makes you feel WOW - I did it or some one did it & I wish I could do it . recall some of those moments and put them together ... possibly you'll get a clue,
What you are consistently enthusiastic about; what makes you feel happy; how much effort is put into it & why is it a WOW! is it persistent?

My story - When i saw Superman movie, i got to know about the computers and how it's being used to communicate & rescue people. That time I set my goal - I want to get into Computer science engineering; while in engineering, Terminator movie inspired me with all those gadgets; started digging deeper into devices and their drivers; shifted focus to high performance computing, which was my major during masters... This helps me in my current work.
I'll cut my story here :-)

You can start off with one area and set it as a base to stand & periodic review of where you stand in terms of your interests and work towards them.
This is how i go- I am agile & socially responsible - I make careful choice with some calculated risk. But always ready to face the unexpected!
'hope this helps

That is a question only you can answer. I would suggest taking a few minutes and picturing yourself in the future. What do you see yourself doing?