Be clear on objectives and criteria.
Get the best out of different types of thinkers by letting others know these objectives a few days before a brainstorming meeting. We all work differently and some will come to the meeting with ideas that they may not have had as a group.
Go off site to get people thinking out of the box.
Take breaks to embrace side conversations & jokes. Keep the energy flowing.
If it relates to a product, have it in the room, sample it, look at it and hold it. Talk and think about its uses and potential.
Listen and write down everything.
Look for parallels among unrelated ideas, there’s a reason they surfaced, so is there a common thread?
Beware the peanut gallery and group mentality. Groups can tend to eliminate all conflict resulting in watered down creative. Sometimes one negative comment can lead the group down a negative path. Move to another subject or idea, but don't rule out these ideas during brainstorming. Mind out the strength in all of the ideas.