3. Don't be afraid to tinker. While the philosophy behind Six Sigma is, or should be, sacrosanct--focus on the customer, reduce defects, streamline and improve processes, evaluate continuously--you needn't treat the tactics and tools as if they're set in stone.

Many big companies, including Honeywell and Textron, have their own internal "brands" of Six Sigma that have been tailored to their line of business and oftentimes combined with Lean, another manufacturing technique designed to weed out non-value-adding subprocesses. Other organizations fine-tune the DMAIC model as needed. Chase Financial, for example, added a step called "implement."

At the toolset level, Raytheon's Debrecht says his teams have wide latitude when it comes to suggesting which measures are appropriate for which projects. "We use brainstorming, value mapping, fishbone diagrams and something we call the 'five whys' to help us get to the root cause of an issue," he says. Textron's Bohlen gives that approach a thumbs-up. "Six Sigma is a system of tools," he says. "There's no prescribed set. You have to determine what you want to bring to your workforce before you choose your tools."

One word of warning: A cautious CIO might be tempted to try a little bit of Six Sigma here and there to see if it works. That's a mistake, says Costa. "We tried too hard to go part-time on some of this stuff, so projects were taking too long. Now we try to focus black belts full-time on a project, and in most cases we're seeing between $1 million and $3 million in benefits," he says.

4. Don't get bogged down in numbers. Like any other measurement-based system, Six Sigma can be driven into the ground by too many numbers. "All that statistical analysis that the black belts use, all those data points don't add up unless you understand what you're measuring," says Gartner's Light. The "define" phase in DMAIC is, in his opinion, probably the most important part of the discipline, and it's the one that involves the fewest metrics. "Chartering the team and specifying who the customers are and defining what a good experience is and what's a defect, that's where the value is," he says.