Mousing your way around the interface to find commands and tools is pretty old school. Cinema 4D has a great shortcut list to speed up your workflow. Your favorite shortcut not listed? Add it to the comments.
Brings up a command line where you can start typing the name of a tool or function you are looking for and it will populate.
2) Polygon Pen - "M~E"
Now you can model faster than ever with this Swiss Army Knife tool in Cinema 4D. Create and edit existing geometry without switching modes.
3) Extrude - "D" Button
Extrude polygons, edges, and points of a polygonal object.
4) Extrude Inner - "I" Button
Polygons extrude inwards from edges.
5) Frame Selected "S" Button
Frames selected object in your scene to the middle of the viewport.
6) Project Settings - Command/Control - D
Brings up your Project Settings to change FPS, Max time, Dynamics settings, and Keyframe options.
7) Viewport Settings - Shift - V
Brings up the Viewport Settings. Allows you to select/deselect a variety of GUI options.
8) Undo Camera - Command/Control - Shift- Z
Undos Cinema 4D camera movement if you accidentally moved it while working.
9) Render Settings - Command/Control - B
Brings up Render Settings for your project and allows to make changes to project size, formats, effects, multi-pass, etc.
10) Hiding Axis Bands - Alt - D
Axis Bands in your way while modeling? Switch them off and on to get a better view.