Most meetups are around 2 hours long. Polling your members for feedback is a great way to nail down an agenda format moving forward, but feel free to adopt the below format for your first few.
Also note, that moderating discussion is a challenging thing! Make sure questions asked are relevant to the entire group. If someone has a particular question about his or her specific strategy, it would probably be best to discuss at the end of the event.
There are a variety of topics that you can choose from, be it a marketing staple like content strategy, or a newer trend. Take a look at some popular starter ideas below:
Check out the HUG content library for full presentations.