The Information and Communication Technology (ICT) sector including data centres generates up to 2% of the global CO2 emissions and data centres are estimated to have the fastest growing carbon footprint from across the whole ICT sector, mainly due to new business such as the cloud computing and the rapid growth of the use of Internet services. The European Code of Conduct for Data Centre Energy Efficiency programme is a voluntary initiative created in 2008 in response to the increasing energy consumption in data centres and the need to reduce the related environmental, economic and energy supply security impacts. Companies participating on the Code of Conduct have to adopt best practices for energy management in data centres. The present report supplements to the Code of Conduct and present the updated (year 2018) version of the Best Practices. This report is provided as an education and reference document as part of the Code of Conduct to assist data centre operators in identifying and implementing measures to improve the energy efficiency of their data centres. A broad group of expert reviewers from operators, vendors, consultants, academics, professional and national bodies have contributed to and reviewed the Best Practices. This report provides a full list of the identified and recognised data centre energy efficiency best practices within the Code of Conduct. Customers or suppliers of IT services may also find it useful to request or provide a list of Code of Conduct Practices implemented in a data centre to assist in procurement of services that meet their environmental or sustainability standards.