Concluding a session can be tricky. Sometimes it is just a matter of recognising that the session is finished.
Ted Scott, a business leader in my community, has been heard to say, "I think that we actually finished a while ago, we just haven't stopped yet." Don't go on and on and on. Draw discussion to a close. If people want to keep talking, give them the opportunity to do that while letting others go.
In other cases, you need to draw the session to a logical conclusion. Don't expect this to just happen. As the facilitator, you need to bring it to a close.
...Geoff
www.performancepeople.com.au