Prepare content in advance if necessary.
Importance
This is especially important while meeting strangers.
Most people do not want to be burdened by an unsettled, harried individual - they are wary of getting tangled in unsavoury business.
General technique
Concentrate on the high order bits: the important matter. Solemnly recognize that exchange of information/ expectations is the most important point of the meeting and determinedly focus the intellect on it.
Suppressing inopportune reactions
It may sometimes be inopportune to feel or display laughter or anger or nervousness.
Use breath control. (PraaNaayaama)