Informal observations give the best indicator of group process.
The formal meetings are critical. They can be a big help and often make the difference between success and failure. My first quarter I did not monitor the groups close enough and had troubles that got bigger than they should have. I think that since then I have tried harder to really see what is going on within each group. I also try to make it more known that if someone is having trouble with his or her group then I am available to discuss it.