Mild introvert here. I've had better luck focusing on 'singletons,' and catalyzing the formation of new conversation groups, instead of trying to work into an existing duo's conversation.

A few years ago I stood alone at a big "networking breakfast." I barely knew anyone.

It popped into my head: Pretend you're the host -- make 'your' guests feel welcome.

Looking around, I spotted another singleton. Smiling, I stuck out my hand, introduced myself, and started doing the ask-questions routine (being careful to make it a conversation and not an interrogation).

A few minutes later, I saw another singleton coming near. I invited him into the conversation and introduced him to the first guy. Both of them seemed glad to have other people to talk to (and when I ran into them at later meetings, they each remembered me). Eventually I disengaged and moved on.

I was amazed at how comfortable that felt, seeking to serve others' needs instead of my own insecurities. I've been using that basic approach ever since. It works every time. My young-adult kids report success with the approach as well.