I have 6 months to prepare for placement. Basically, I'm a Computer Science student. How and what do I study?

Let’s first look at what all skills you need to have for campus placements. Assuming that the companies are hiring for a software developer role, you would need:

1. Proficiency in any one programming language.
2. Very good problem solving skills and knowledge about data structures and algorithms like stacks, linked lists, searching, dynamic programming, etc. For complete list, can visit the syllabus at Programming Pathshala’s website and can follow that
3. A good project for your resume. Would suggest a full-stack project.
4. Maintaining a good CGPA (>=8/10 in Indian context) would be a good idea.
5. Clean coding skills, design principles and patterns (Part of Low-Level Design)
6. Subjects in Computer Science like Operating Systems, Computer Networks, DBMS.

For roles different from SDE, there might be some other things you need to do. Statistically speaking, SDE roles are the most common. So, it is a good idea to stick to those.

Now, all this might seem a little daunting, specially if you have to do it by yourself in 6 months. But, ideally it is very much possible if you put in the efforts.

Apart from that, if you think you would require guidance from alumni of top tech companies, do selected problems from each topic that cover all the subpatterns of a topic, give mock interviews and/or need referrals, you can also opt in for a 6-month interview preparation course with us at Programming Pathshala.

Note:
After considerable discussion with Bharat Khanna, co-founder of Programming Pathshala, I was able to formulate this response. Who also happened to be an ex-SDE at Tower Research and a codeforce candidate master.