Edit: I recalled the difficulty I had to hit the right links for my interests when I passed first year. So I have decided to include some links and references in the answer.
This answer is for the students who come to college without much exposure on the various fields in CSE.
In the first year, during college participate in as many club events (try out Web Dev, App Dev, Competitive Coding, Paper Presentation). After you have seen a bit of everything, it will be easier to realize your strengths and weaknesses. It is completely all right if you have a lot of weaknesses as long as you have a single strength. During the holidays you can enroll yourself in a MOOC course to see if you are really interested in the topic that you feel you are good at. Below are some links to check for the more powerful MOOCs out there.
Which is the best MOOC for learning CS?
If you are reading this, then thumbs up, you are already part of a great Community, Quora. Read on topics here. A simple search on the web will lead you to numerous blogs which shall guide you. Join online coding platforms like Codechef, Hackerrank, SPOJ for they let you grade yourself relative to the entire world.
During the summer holidays which is very extended, you can give Google Summer of Code a try. You shall learn a lot out of all the research and open-source contributions that you will make in the process. A batchmate, friend and a guy who completed GSoC after his first year, Pawan Dubey has curated a pretty nice answer on how to approach GSoC.
Pawan Dubey's answer to How can I prepare for GSoC 2015?
In the course of second year, keep reading, keep coding and keep learning. During the winter break, spend time looking for opportunities where you can Intern for the upcoming summers. See the requirements of the Company/University which have positions for 2nd year interns. Working in a Company/Start-Up shall give you a real insight of how the Corporate Culture is. For some it might even make them realize that they are not meant for desk-jobs. If you are research oriented, try working under a Professor on some active project. The information about Professors and their topics of interests can be obtained by doing a simple search on the University Website. If you want to do a technical internship abroad, there are organizations like IAESTE to your aid. For non technical work there is AIESEC. Also, the summer break is also the time where you can hone your interview skills if in case you want to prepare for the upcoming Campus Interviews(for Microsoft, Amazon, Goldman Sachs), early 5th Semester.
Third year and onward, you can have a look at your resume and decide for yourself what you lack. You shall also learn by looking at your peers and that should be enough to guide you.
I have mostly seen that people lose out due to lack of awareness and not because of lack of ability. So it is very important that you develop the skill of looking out for opportunities as early as you can.
Good luck.