What are the technical details of travelling to Cuba (in 2016) [closed]

[There are multiple questions and answers here on SE about travel to Cuba, but they are all written before the opening - I am asking about late 2016]

I am considering travelling to Cuba for educational purposes, and I have identified flights and hotels, etc. My question is about the technicalities:

If you fly from a non-US airport (for example, Mexico City) to Havana/Cuba, what paperwork do you have to have with you when you arrive (as a US citizen or German citizen, either way, because we have both in the group)?

I assume a passport, of course, and better bring some cash, but what do you need outside of this?

Do you need any health insurance documentation, and how would that look? Any upfront arranged visa or other paperwork? Or can you just walk from the plane, pay whatever fees, and be fine?

There are many sources on the web, I spend days reading around; but most are obsolete, and many are contradicting. I'd prefer to hear from someone who did it, maybe in the last three months, in the current political situation:

What was really needed when you arrived? which sheets of paper, and how did you get them?