Thus, one possibility is to build a skeleton out of Box objects. This has significant advantages because the boxes are easily visible and renderable. You can play with and animate the full skeleton with the attached mesh hidden - and then hide the boxes and unhide the mesh to render. There's a lot to be said for this approach, and it's standard practice with many MAX animators. On the other hand, you can build the skeleton out of Bones, as I did here.
Bones are non-rendering objects that are, compared with boxes, hard to see and select.
Here's where things get confusing, so take it slow. There are other IK alternatives in MAX, but Bones are the best choice by far. That means that if you want to use boxes in the skeleton, but want to use IK, you have to put Bones inside the boxes. In the end it's workable, because you can hide the Bones inside the boxes, but it's a hurdle for the newcomer. The following image shows this kind of setup for the lower body.