We try to hold one every other month and staff send me agenda items that can cover anything and everything. As our firm is specialized in IP only and all staff does everything, agenda items for discussion are plentiful as we made it a point that agenda is set by all. Sometimes our staff meeting is purely to discuss interesting cases people (lawyers and staff) are involved in to keep everyone in the loop and share things of interest in the file/case so everyone learns or can give feedback.
