What would you have done differently in your datacenter(s)?

I've been put in charge of a datacenter network overhaul/redesign at work. I've got basic redundancy factored in, Out of Band management, stacked switches, OSPF, VRRP, etc. however this is my first time implementing a network of this size/importance.

what are some things that you wish you had accounted for (or taken the time to set up) before the big turn-up? I feel pretty good about how I've set things up, however I really would like to avoid being up at 3am (sobbing) because I didn't do something and now I have to go to the DC. I've been reading Cisco docs (and others) about Networks + Network Operation -- however real life feedback is always best.

Thanks in advance! Long time lurker, first time being able to make a post w/o breaking the rules (long time homelab user.)