Right off the bat the cast talk about personal failure stories and then they ask if anyone in the audience wanted to share one of their own. One person did and then the play moved on.
There is also a simple survey. Who loves their father, hands up. Who hates their father, hands up. etc
Later on, the audience is asked to write down a question on paper/pencil provided that had gone unasked/unanswered of their father (whether alive or not) These are collected.
Finally, certain number of volunteers are asked to come on stage to take part in a ritual. It doesn't involve any talking by the volunteers, just a simple (but meaningful) ritual and then they leave the stage once done.
You don't have to participate in any of these three things if you do not wish to.
I'm not a fan of audience participation, but everything made sense in the context of the play and I felt it was effective and well timed.