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.
Because you rarely get things right the first time.
Access context sensitive menus quickly.
Toggles between Live Selection and last tool used.
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.
Thanks to @demafleez, @Pgoski, @ Motionworks, @JosefBsharah and @leehoffguy for their suggestions.