This is a very insightful tutorial on how to pair fonts. What I love is the level of detail it goes into to let you understand how to look at several fonts and understand whether they will go together or not.

A finer understanding of the parts of type is the starting point and then looking at how certain parts of the font’s construction can clash or complement one another.​ Of course, we’re not always after uniformity so there is a great section on how to use differences and contrast to your advantage.