Is Sass somewhat of a mystery to you? How does it work? Why do some say that it is better then CSS?
Cover all the basics. Nesting, parent/selector reference, variables, extends and mixins. Then progress into Sass Scripting like, operations, functions and directives.
Sass 101 - A Newb's Guide is more then just a deck, it's an interactive introduction to Sass. As an added bonus, download the PDF and each code side not only contains an awesome Sass example, but links to a long explanation to help you get started and a link to SassMeister so that you can interact with the code example.