First we look up DVD RIPPING and learn how to do that. Mind you we must obey copyrights and all that so this is all I'll note here.

Next the clipping is done with your choice of video editing. What I use is Virtual Dub but I offer no tutorial on its use. Some ask why I don't and it's simply because I would be duplicating web content.

In short you rip the dvd. I then can clip with virtual dub the pieces I wanted. Next I can build my compilation video by opening the first piece in virtual dub and adding the others.

This is not an offer to teach the above but to give a starting direction. Be sure to set aside about 10 hours or more time for each hour of video you want to make.
Bob