I've collected all of the videos that Doug has done (since they are rather scattered through a long thread) and linked them here. I've also added some additional videos that I've done which cover more or less the same ground but just in a different format - and they are slightly more up to date in some cases as things have been added.

Smiteworks Videos
Introductory video to adding LOS to maps
Secondary method of adding walls using the keyboard
Terrain Usage Considerations
Terrain Discussion
Adding Secret Doors after the fact

Zacchaeus Videos
Adding Occluders - The Basics
Adding Occluders - Doors and Secret Doors
Adding Occluders - Terrain