What should I do to become a great data scientist if I am currently an engineering student at IIT Roorkee and an intern at Nucleus Software, and I want to work with a firm like Google or Facebook?

The primary step to become an excellent Data Scientist is to become proficient in some programming languages. Some of them have been listed below 

• C
• Data Structure & Algorithm 
• Python 
• Java 
• SQL 

Having a basic knowledge of these languages is not sufficient. One needs to become proficient in data structure and algorithms to kick-start a career as a Data Scientist. Apart from programming, you will also have to broaden your knowledge base related to Math and cover topics like Discrete Mathematics, Linear Algebra, Statistics

IT giants like Microsoft and Google don’t just offer jobs to anybody. Here are a few guidelines to secure a core data science job 

1. The primary step, as I said, is to become proficient in programming languages. You can begin with the easiest, Python. Next, you can target R which is also open-source.
2. Next, you need to try your hands on SQL which will require lots of experiments with data.
3. Statistics and probability are considered the soul of DS and it’s very crucial to become proficient in them. You can learn it from MIT courses. 
4. ML or Machine Learning is also an indispensable part of DS and one requires enough Mathematical knowledge to learn this.
5. You should also learn Natural Language Processing
6. Try to complete dummy projects available on the internet. One such project is The Home of Data Science.

Anyone who follows these guidelines will reap the maximum benefits and become a successful data scientist for sure.