How we change what others think, feel, believe and do
Take what they have said and following the argument to subsequent steps. What might happen next?
Consider what they say as a cause and explore what this might cause, using cause-and-effect reasoning.
Then reflect back what could happen next.
You can also reflect back as a question, to check whether they have thought of everything.
If you are seeking to move the conversation towards a particular end, then seek to extrapolate in your desired direction.
What you say can either be as a supportive argument or contrary, for example to warn them of possible undesirable consequences.
Other: I'd like to go to town.
Other: If we do it in blue, it will look good in the sun.
Other: We're going to do the presentation tomorrow.
A constructive way of reflecting what a person has said back to them is do add to what they have said in some way. This helps both testing understanding and also building rapport. If you build something between you, you will both feel a sense of ownership of it and hence will be more ready to share more.
Extrapolating builds the conversation, taking it somewhere else. It gives you a degree of control whilst connecting with what the other person has said.