In this video we create a cylindrical object with a square hole. We however do not start with a cylinder. We start with a Circle mesh with 8 vertices. This is to allow us to have as simple of a starting mesh as possible.
Shortcuts to know (Default):
Shift+A = Add Mesh / Whatever
Tab = Edit / Object modes
E = Extrude / Extrusion
G = Grab / Move
S = Scale
CTRL + R = Loop Cut
Shift+Right Click = Select More Than One
Period (NumPad) = Focus on Currently Selected Object