This is based on a video I watched of an IIT student who got placed as SDE in Microsoft.
There is a program called Microsoft Engage Mentorship Program which Microsoft conducts each year. They select students across the globe who are curious about learning new things and making projects.
How to apply
Keep an eye on Microsoft's career page, they post a portal link where you can apply for the program.
After applying, next what?
After your application, the employer goes through your resume and if selected, you receive a coding test link.
Main part of selection: How to clear coding round?
The student got 2 questions:

1. DFS based question
   
2. Graph using DP

One tip
If you're stuck in any part of the code, ask the interviewer for hint. Most of the time, they do give you a hint. Make use of it and move ahead with the coding part.
Round 2
In Round 2, two questions were asked about DP and Strings.
Round 3
After 4 days, the Round 3 was conducted for those who cleared Round 1 & 2.
In the Round 3, the student was asked to introduce about himself and tell about the projects he has worked on / currently working.
After that, he was asked about system design.
TIP
Along with the coding, do have knowledge about how to design a large-scale distributed system. The student had a discussion with the interviewer for half an hour regarding large-scale distributed system. Questions asked were mainly about the working and implementation of large-scale distributed system.
Q. If I am in my third year, how can I join Microsoft in 4th year?
-> Practice DSA questions from leetcode
-> Practice CP from codechef
-> Have a strong resume with projects
How to get from program->internship->placement? Once selected for the program, you will be assigned a project and you are supposed to complete within a deadline under the guidance of a mentor. Based on your performance you either get direct internship, or you will be given few coding questions and based on your performance you get selected for internship. After you get an internship at Microsoft, there is a high chance you might get PPO. Just make sure you perform your best in internship.
How much time is needed to prepare for coding rounds?
If you solve leetcode questions daily, 6-8 months are sufficient.

When will you start your preparation?