Pictures
Since we all carry a camera with us everywhere we go, a few pictures of the back of each server, each switch, etc. in the "before" state in the old data center can be worth its weight in gold when it comes to the "after" data center, given the propensity of labels to not be updated when things change, fall off due to the heat inherent in a server cabinet or in transit, etc.
I first recommended this 15 years ago, before cell phones had cameras but digital cameras were readily available. It took a little cajoling, but the guys who executed the move thanked me profusely afterwards. I've since always brought this up, and modern smartphones mean there is no excuse not to do it.
Biting the hand that feeds IT
