Affinity diagrams or charts are a simple way for a group to cluster qualitative data and come up with a consensus view on a subject. Alternatively they can be used simply as an aid to stimulate debate.
Each member of the group is issued with a stack of post-it notes and a pen. A subject area or a "goal statement" is defined and everyone asked to write down any ideas they have on the subject, one idea to each post-it. A limited time is given (e.g. 5 minutes). The post-its are then stuck onto a whiteboard or sheet of paper and an attempt is made by the group to invent headings under which to cluster the ideas.
The post-its are moved to the appropriate group headings.