One of the biggest complaints I see on retrospective is that action items are not followed up.

I'm quite happy to see that on my current project people take it very seriously. There's actually a wall with the retro items to be followed up (To Be Done TBD) and when they're done we move them to the \o/ happy/done column. During the following retro we go through them. Another important thing is to assign owners to these items! yay for the team!!!

Foto: Henrique Rezende