I took a basic 40-hr Reverse Engineering course a few summers ago. Whole teaching us to use IDAPro, the instructor demonstrated, rather quickly and without explaining much, how to label certain variables in the ASM as members of a structure, basically equivalent to a good old fashioned `struct` in C/C++, and treat them as such wherever they are seen in the rest of the code. This seems rather useful to me.

What he did not cover, however, was how to identify a structure. How do you know when a group of variables does in fact constitute a structure and not just a set of related variables? How can you be sure that the author used a `struct` (or something similar) there?