The 'Ankle Isolation' Guard Pass is one of the most effective I know. I first saw my instructor Roger Gracie using it several years ago and was impressed by how the technique shut down an opponent's hips. I spent about a year playing with the move and I'm at a point now where I think I've figured it out. Let me know if this helps you or if you have any details to add.
The Fundamentals of BJJ, including Guard Passing, are covered in The BJJ Building Blocks course by Roger Gracie Black Belt Nicolas Gregroriades