Here is a format for Lean Coffee that a group from AgilePDX 
is using:
Step 1: Everybody writes down proposed topics on stickies, placing them in the center of the table. Take as much time as needed, but typically takes only 3-5 minutes (or whenever coffee is ready). Step 2: Each topic is briefly described by its writer to get a flavor for the subject (15-30 seconds typically per sticky). Step 3: Each person gets five votes which they indicate by marking the voted-for sticky with their Sharpie. Mark with a plus + if you agree with the topic and want to discuss it, or a minus - if you disagree and want to discuss it, mark it with a dot if you want to hear the discussion and maybe join in. You can put all votes on one, one across many, however you feel. Each mark counts as one vote. Step 4: The top vote-getting stickies are placed in the ToDo column, ordered by the stickies with the most votes at the top. In an Agile fashion, we'll use groupings of ToDo, Doing, Done and Lessons learned. Step 5: Each of these stickies are discussed for 5 minutes, most votes first. The facilitator takes a quick "Cesar" (thumbs up/down) vote at the five-minute timer, and she moves on for three more minutes if the discussion still has majority interest. When complete, move the sticky over to the Done column. Rinse and repeat. Step 6: wrap-up thoughts at the end - what one idea or person did you most enjoy, then break for home/drinks/cover.