there's a lot of different sources you can use to get information about MBAs and I would distinguish them in 2 buckets:
- Information about the program: courses, professors, student body, post MBA employment opportunities, campus...you name it. For these you can relate to the official brochures produced by the schools. I would read carefully the "Employment reports" that give you data on where the graduates of a specific class ended up working full-time (in terms of industry, company, geography, etc). Another very useful source are alumni, a coffee chat with someone who attended the MBA would give you the chance to interact with someone who lived the real experience and talk to you about the pros and cons of the program.
- MBA rankings: they give you the chance to "compare" different schools, the most important are published by the Financial Times, Bloomberg Businessweek, The Economist and Poetsandquants.com. These ranks will give you an idea of which are the "best" programs worldwide but don't forget that they are based on a set of criteria (like how many alumni are employed 3 months after graduation, their weighted salaray n. years after graduation, their satisfaction rate, etc.) that is not consistent from one to the other, so the same MBA can be in different positions in different rankings, just to give you an example in 2016 Insead was ranked 1st by the FT and 13th by the Economist.
Out of the many ways you have to assess the best MBA for you, I'll give you my view based on my personal experience: if you aren't sure about your future plans go for the program that inspires you the most, if you do have a future plan in terms of what job you want to do and where you want to work, consider the "geographic factor", which is more relevant than what you will read in most of the publications. So if you are interested in working in Venture Capital in the Silicon Valley, for example, try to get into an MBA that is in that area, the networking opportunities and the interactions with companies located there are obviously going to be more frequent than if you study somewhere else and that will be a key factor in your future job placement; this obviously doesn't mean you can't get a job in the Valley if you study in NYC or Chicago but it could be a bit more challenging due to the distance.
Hope this helped.