We present here the first of ten units of study used by the author to train beginning graduate students and advanced undergraduates for further study in the general topic of combinatorial algorithms. This unit of study focuses on mathematical concepts used to linearly order sets of objects. Our general approach is to focus on the "geometric" theory of algorithms by which we mean the use of graphical or pictorial ways to understand what is going on. This approach is both fun and powerful, preparing you to invent your own algorithms for a wide range of problems.