Paradigm Shift

What is it?
It is a shift in perception from one experiential plane to another. It re contextualizes our experience based on new definitions totally unconnected with earlier ones. It might be something that is desirable (think about some experience like love or compassion) or something that is harmful (think about some one being vengeful after a bitter experience).

What does it cause?
A change in perception, and consequently a change in relationships. Relationships dont refer to just people but to how we hold our thoughts, what we hold as thoughts, how we view material possessions and how we relate to people (not just dear ones - or shall we say, who become our dear ones).

What causes it?
I heard an Isha meditator narrate his experience during his yoga program. It was not yet time for the class to start, but was close to starting time. He went outside the hall for some reason and he saw someone arranging the slippers strewn outside the class hall. He assumed it was a volunteer and returned inside. Later, he was shocked to realize it was the person conducting the class himself. He mentioned "The class wasn't necessary. That once incident did it all!"
So, the short answer is, one can never say. It depends on multiple things - the event itself, the disposition of the perceiver (his body, mind, emotions and may be energy) and few other criteria possibly. Two people can see the exact same thing and perceive it completely differently - may be even in diametrically opposite directions.

What does it mean to us?
It means that once it happens, we will relate to our surroundings differently. Think about the lady who scolded her brother just before they were separated in a concentration camp and never saw him again. She decided that she would view every encounter with another person thereafter as the last encounter. Contrast the difference if she had not made that decision versus after the decision. And it is important to realize that it is not a decision of the mind alone. It is possibly a change in the entire chemistry of the system that left her transformed completely.
So if something like that happens to us, we may drop some material things, move away from certain people, attract certain people, do different things, do things differently, quit your job, get a job if you were idle - a million things.

You cannot *ever* be prepared for *what* causes the paradigm shift. Life is too vast!
However, you can be prepared, to an extent, for *what you will become* if it happens if you realize that these changes will happen!

How can you facilitate one?
(For all purposes, I am not interested in a counter-productive paradigm shift). 
May be it will anyway happen to you.
But I remember one of Sadhguru's quotes that sums up how one can keep herself to facilitate this.
"The way we think is the way we become. Whatever you hold as the highest, naturally all your energies get drawn towards that."
So one can say we can make a decision on what we hold as the highest.