Standards

Standards are typically global in scope and are not to be confused with regulations, which are often local in scope. Standards are written so that you, as a data center professional, don't have to re-invent the wheel when it comes to determining how to do things in your data center. You can take a standard and tweak it to meet your specific needs better, and not worry about being in violation of laws. Some standards are very loosely written, while others are quite specific.

Process Standards
ITIL is probably the most globally accepted standard/recommendation for data center and IT processes.

BICSI is basically a standards body that was created after the breakup of the original AT&T/Bell Labs corporations. They have a comprehensive "How to Data Center" standard, called 002, and the latest revision was in 2014 (so it's really called 002-2014). It covers a very wide range of subject matter.

Cabling
TIA (Telecommunications Industry Association) publishes two main standards for data center cabling. TIA-942 is the overall cabling structure for your infrastructure, and TIA-606 is the standard for labeling said cables.

For those who can't spend the money on the standards, let me paraphrase TIA/EIA 606-B for you -> Put the endpoints on your labels. Stop making serialized cable labels that you then have to go look up in a database. Granted, the standard goes into a lot of detail about best practices for abbreviating your endpoints and focuses a lot on size, material, readability, etc, but the punchline is still the same. Make your cable labels such that a human can understand the naming scheme well enough to look at a cable and immediately go to either endpoint without having to consult a computer.

Energy Efficiency / Cooling
ASHRAE (American Society of Heating, Refrigeration, and Air Conditioning Engineers) has published TC9.9 (Technical Committee 9.9) recommendations for cooling your data centers.

EU Data Centres Code of Conduct for Energy Efficiency is a great, freely available standard written to help you identify areas to focus on to improve energy efficiency in your data center.