Set up a 'retrospective mailbox' at the beginning of the iteration. Whenever something significant happens or someone has an idea for improvement, they write it down and 'post' it. (Alternatively the 'mailbox' can be a visible place. This can spark discussion during the iteration.) Go through the notes and discuss them. A mailbox is great for long iterations and forgetful teams.
Brainstorm what worked well & what to do differently and pick the top initiatives Source:
Head 2 flip charts with 'Worked well' and 'Do differently next time' respectively. Ask your participants to write concrete proposals for each category - 1 idea per index card. Let them write in silence for a few minutes. Let everyone read out their notes and post them to the appropriate category. Lead a short discussion on what the top 20% beneficial ideas are. Vote on it by distributing dots or X's with a marker, e.g. 1, 2, and 3 dots for each person to distribute. The top 2 or 3 become your action items.
Gauge participants' satisfaction with the retro in minimum time using smilies Source:
Draw a ':)', ':|', and ':(' on a sheet of paper and tape it against the door. When ending the retrospective, ask your participants to mark their satisfaction with the session with an 'x' below the applicable smily.