If you are having a meeting please have an agenda and control your meeting
One of my big complaints is that many people do not know how to control a meeting. You see this more in meetings where outside consultants can hijack the meetings and steer them away from the original meeting points because they can and they see a chance for more business.
The key to running a good meeting is to have an agenda and stick to it. It's actually very hard to do this because as a meeting chair, you don't want to be rude and tell someone to keep to the agenda. Guess what? As meeting chair it's ok to do this and others will thank you.
I'm going to borrow a tip from a colleague:
Everything is either:
1. An action (write down who for, what and deadline)
2. An update / fact (write down for future reference)
3. An open question (see (a))
4. Something not currently relevant (write down under a section titled “park” or (“to come back to)
Number 4 on that list is probably your most powerful tool as a meeting chair. If someone starts to go off on a tangent you let them have their say for a minute or two, make a note of it then say 'OK, That's interesting and has been noted. Let's move on'. If they come back to the point you just point to the note in the meeting minutes and say 'We've noted that as a parked comment, moving on'.
This way you can stick to the agenda and keep the meeting focused.