NU students are extremely time conscious and often unwilling to give up more than one hour of their evening study time. If the formal session is only an hour, with those especially interested able to stay longer, the time commitment will not discourage attendance. You are encouraged to discuss the presentation in your invitation conversation. Ask the students about any particular perspective or emphasis that their group may prefer. This is not to imply that you cater to the audience and make one's presentation more effective to a particular group.
Intriguing titles can be helpful.
Experience shows most students thoroughly enjoy Firesides, but getting them to attend is the challenge. Titles and topics can often stimulate the needed interest. Naturally, you choose the appropriate format. However, it is suggested that variations from a straight lecture can be effective. Handouts, slides, demonstrations or any procedure that actively involves the participants is often a plus.