How should I prepare for a Data scientist interview at Facebook,Google,etc?

Leading multinationals such as Facebook, Google etc. thoroughly tests the technical as well as lateral thinking skills of an individual before recruiting them into their business units. These companies put in a lot of emphasis on problem solving wherein the questions asked in the interview are extremely open-ended questions; and the candidate’s approach to problem solving is highly tested.
Other than these, the data aptitude of the individuals is tested thoroughly as well in terms of how the candidates are able to leverage rich data sources to extract information out of them.

Moreover, theses companies require to have alteast a Master’s degree in most of the cases so have that in mind while applying.

I think you should have the education, experience, and individual competence. You should already be in a higher quantitative percentile, know multiple programming languages, and have a keen business sense. My kind is an economic intent for management. You should be able to join the team, work with partners and quickly understand their business model. To provide business value, you need to use the Facebook product and services. You need to do market research on this one, among competing products and their brands. You should be in the mindset to contribute to the company in economics. You particularly just have this technological advantage.