This short book summarises the process of data modeling and its diagram creation for NoSQL databases, such as MongoDB and Couchbase, which do not have strict rules, unlike the SQL ones. It covers the important parts of deciding how to handle one-to-one, one-to-many, and many-to-many relationships in various scenarios, based on bound and unbound cases of data growth, and the frequency and type of expected updates on the records. The book contains several examples to explain the concepts.
I have compiled the book with the material already available on my blog for free.