Check the manager tools podcast, they have some really good tips for this. IIRC a bit spread out but there are specific meeting episodes.

A big one is that you can empathize with the need to discuss things in general, and also emphasize the goal to focus on one topic, and if you do both of those at the beginning of the meeting you are more likely to get what you want.

Another big one from my own area of specialty is that people aren't always in control of their interactions despite best intentions. There are "resting/venting" and "party" combinations that naturally occur when specific perspectives come together, even when the individuals in isolation consciously want nothing of the sort.

So A) another good reason to stay away from too much blame and B) possible hint that meeting composition can be helpful to look at as well.

Good luck.