A neat feature of DFP is the Change History Tool, which allow you to see when changes were made and who made them. This tool is a little bit buried in the interface, but can be accessed under the Admin tab.
On the Change History screen, you can see who made each change and when it was made. The information can be a bit overwhelming, especially on large sites with multiple traffickers, since absolutely everything is tracked. However, there are a few filtering options that makes things a little easier.
You might not need the Change History tool every day, but when you do, it can be invaluable. If there are multiple people on your team, spend a few minutes playing with the Change History tool to get a feel for how it works so you’ll be prepared for the day when things go horribly wrong and you’ve got to sort through the wreckage.