Applied through their Insight Week, so this review will focus mainly on their Assessment Day for conversion (typically you would have to submit an online application, do the Plum test, a HireVue, and the interview for one hour with Team Leaders).
Online Application: If you are applying for Global Data, be technical! Send them in examples of your previous data/coding work (I submitted some of my old programming reports from class). Not sure if they review it, but if they do, it's good to have these examples of previous work (definitely puts you at an advantage). They ask questions on the application for a reason. Do not copy their company language and try to sell it back to them, tell them truly how you understand Bloomberg and what intrigues you by their work. Cover Letter is not that important. Languages are CRUCIAL. Minimum 2 languages (most people will speak more than two).
Fit is everything for Bloomberg. Seriously. They can teach you all the programming and finance (and trust me they will invest a LOT in you if you join them), but the fit is something they have to identify first and foremost. Everyone is incredibly bright, collaborative, and nice at Bloomberg, and willing to help.
A part of your application is the one-hour long Team Leader interview. It is rather normal (nothing technical), but they really want to break down your experience and understand your motivation. In this interview, you sit across two Team Leaders (in my case, one from Global Data and one from Sales and Analytics). In your interview, build a story about yourself. In that one minute pitch you will have to tell them about yourself (usually first question), tell them about how your degree and experience tie into your interest in Bloomberg. Tell them why you are interested in Finance (beyond your degree!). They might ask why you decided to apply there instead of an Investment Bank. They might also ask you what you hope to never experience in your workplace. Prepare your STAR responses well in advance! Know their products and services inside out. Really research before your interview (they WILL ask you about their products) and make sure to have cool questions to ask them in the end.
Assessment day: Data Analytics test and Process Re-engineering task. I was incredibly stressed for both, but they were truly not that hard, and here's how to ace them.
(a) Data Analytics test: Multiple choice, on HackerRank, 35 mins to complete, 12 questions. Time is not a problem. Few easy statistics questions (review simple linear regression and averages, yes it's that simple), 1 SQL question, 3/4 Python questions. They accept most applicants regardless of programming experience, so this is really not a deciding factor, but try to score above 50%. Python and SQL: Just review syntax and make sure you can read easy scripts. You will have to correct or fill in the blank for some SIMPLE programs. And then for math, you will be given a simple table and have to calculate easy figures/predict the next value. Review truth tables.
(b) Process Re-engineering: You will be given a flowchart of how they extract and process data for one function and you will be asked to provide three recommendations. Be confident, a good communicator. Be confident in your answers, take notes, and organize your thoughts/points before you express them. Ask questions. Try to recommend that they automate every manual task you can identify. Make sure to verbally express your thinking process: that's what they want to see above anything else here.
