If you're going to do one at your club or something, make it relevent to the season. Eg, now I would be discussing cold weather ops, icing, how to avoid and what to plan for. Get folks back into the performance section of the pilot's manual as a refresher. Never hurts. You could have a section about the expexted wx conditions for the season ie what weather patterns to expect with the typical vis and cloud issues.
(Summer, again bring in the wx issues, performance issues and how to make the trip more comfortable etc)
Nothing like a group think with GPS too. Reviewing how people get the co-ords off the chart and into the magic box.
Refresh folks memory about getting NOTAMs and translating that into something meaningful for navigation.
It doesn't have to be a mega formal arvo/night. Bung on a bbq.
To make it really meaningful, get a summary of the topics printed off so people have an accurate reminder of what they learnt.