Energy Conservation takes many forms. For our purposes we will limit this to the energy you use in your day to day operation, with an aim to assist in the reduction of the total amount of energy you use. Measures that fall in this category include:
Energy Metering with proforma bench marking: Install meters on your energy consumption (electricity, gas, water etc.) and track the amount of energy you use, then benchmark you usage against similar occupations to determine where you fall. This allows you to understand where to concentrate your conservation efforts (if you can measure it, you can control it).
Recommissioning your building to today's standards will lead to substantial savings. When buildings are constructed they are commissioned (a set of operating parameters created by the engineering designers which lays out the way you operate the building (when to turn on the lights??)).
In commercial applications recommissioning generally results in a 16% energy consumption reduction with a simple payback of less than 2 years.