What different approaches do you use in talking with different people? How do you know you are getting your point across?

If I am talking to one person or small group of people .. I try to establish a foundation for what the talk will be about and what it aims to achieve .  Here, I may have prior knowledge of the people that I talk to, which means little more comfort knowing who they are.  If this is the first time and I have no previoius knowledge, then I will spend the first few minutes exploring what could be a good start point for the talk

Anither case which I am experienced with, is when you address a public audience and talk to them about some common intersst topic (as in conferences, seminars, presentatons, ...) .  Here, you have no control on who the audience are, and there may be no prior knowledge of who the audience are.    However , the topic itself will determine to a large degree how you will address this audience and talk to them