Sometimes retrospectives can be slow to get going as team members rack their brains trying to remember events over the last couple of weeks. A simple solution to this can be for the team to maintain a "continuous timeline" which can be used to kickstart conversations in retrospectives.
Here's how we do this at Unruly. We record any significant events on our team whiteboard at standup time or during the day. When it comes to the retrospective, we take a photo and bring print- outs that we can refer to. We also email a copy of the board photo to Aimy, one of our product managers based in our New York office so she can see what the team in London are talking about.
I've included a photos from each team below. When Arber, one of our product managers in London, originally skteched these on the board he chose engaging templates for each team: a Monopoly board and a Snakes & Ladders board which helps keep this activity informal and lighthearted. We log any significant incidents and events -- especially if they become a time-suck live issues -- along with social stuff like team lunches and cakes.
Yesterday I met Chris who has a similar practice at a large investment bank albeit slightly less visual. His team write a daily team log on a wiki page and then refer to the entries over the last two weeks in their retrospectives. I'd be interested to hear if any other teams have a similar practice.