This document is a guide to achieving operational efficiency through best practices in operations and maintenance (O&M). It was prepared by Pacific Northwest National Laboratory for the Federal Energy Management Program. The guide consists of 11 chapters that cover topics such as why O&M is important, O&M management, computerized maintenance management systems, types of maintenance programs, predictive maintenance technologies, commissioning existing buildings, metering for O&M, and O&M ideas for major equipment types. The target audience includes federal O&M and energy managers.