How to be less awkward in a conversation with 3 people?

I always get into those awkward 3-way conversations. There are three people standing around a group. And one person seems to only be talking to me and the third person is left out of the conversation. This makes me feel incredibly uncomfortable.

I picked up a neat fix to this problem. When someone starts to address and only talk to you, you just look at the person that is talking, then make eye contact with the third person (and maybe add a smile). The person talking usually notices and opens up the circle and begins to address both of you. Finally then, you get a proper 3-way conversation.

I was so thrilled to see Bain & Company Chairman, Orit Gadiesh mentioned this similar technique in her interview with Maire Claire. Different context but same idea.