The WSJ has an article about How to Tap IT's Hidden Potential , and many of these same ideas ideas apply to how Green Data Center projects should be executed. In fact, most companies who have green IT initiatives practice most of the ideas in this article.

Simply put, top executives at most companies fail to recognize the value of IT. It can help a company transform data from its operations, its business partners and its markets into useful competitive information. It can be the source of profitable innovations in the way a company interacts with its customers and suppliers. But there is still a tendency to think of IT as a basic utility, like plumbing or telephone service.
VIDEO: IT'S HIDDEN POTENTIAL

The chief information officer's role has become so important that it can now be a steppingstone to the CEO's office. Amit Basu discusses this development and its implications in an interview with the Journal's Carol Hymowitz.
In many industries, IT consumes a significant amount of capital expenditures and gross revenue. Though recent research has shown that managing IT well can significantly increase a firm's profits and deliver substantially higher returns on IT investments, its potential is overlooked, and even its workaday application is often mismanaged.
The result isn't just missed opportunities -- it's also wasted money. Analysts estimate that hundreds of billions of dollars are blown every year on IT projects that fail to achieve the desired goals.

This last point can include energy savings projects when you don't have a monitoring system in place to measure successes and failures.

Here are the points in summary:

Begin with IT literacy -- and commitment -- at the top

Hire an IT leader who sees the big picture

Create demand for IT solutions

Make sure nothing gets lost in translation

Rationalize IT spending

Create an IT portfolio by evaluating risks and returns