Few questions reveal as much about the customer experience as: “How likely are you to recommend this company’s services to a friend?”

To find out the answer, leading companies such as Charles Schwab, Apple Retail and Allianz use Net Promoter Scores^® to gauge the quality of their relationships with customers. But are these scores accurate and reliable? Not always.

The chief executive of one business-to-business (B2B) company, for instance, hired market research firms to gather data about its promoters and detractors. The research firms carpet bombed the company’s customers with surveys. But the resulting scores proved volatile and undependable. Response rates were low, which increased random variation from one period to the next. And no one could tell exactly which individuals filled out the surveys. Indeed, subsequent analysis showed that few senior decision makers or influencers ever took part. So the scores didn’t accurately reflect key individuals’ attitudes and actions.

Data problems like these can undermine trust in a Net Promoter System. Yet many companies have learned to compile accurate, trustworthy scores. The precision and granularity of those scores enable them to learn more—and quickly—about their customers’ opinions, so they can take appropriate action.

Here’s what they do to mine the best data:

Survey their clients often: Many leading companies survey a sample of their customers every week. Nearly all issue reports every week or month. Frequent surveys enable you to monitor scores for unexplained variation. They also allow you to test new approaches.

Be consistent: Different survey methods can produce radically different results—so it’s essential to find one method that works best for you and stick to it. This applies even to seemingly trivial variations, such as the wording of survey questions. Every change needs to be tested first to see if it affects responses.

Track participation: Higher response rates lead to more accurate survey scores. Anything less than a 40% response rate for business-to-consumer (B2C) and 60% for B2B enterprises is a red flag.

Identify key client groups: The most important thing is high response rates from your core or target customers—those who are most profitable and whom you would most like to become promoters. Retail banks, for example, find it helpful to survey customers by segment, so that the responses of their most profitable clients aren’t drowned out by those who are only marginally profitable.

Prevent bias: Create conditions that encourage respondents to give honest answers, even if they’re negative. If a participant is embarrassed or fears alienating a potential vendor, he might avoid providing critical feedback that could help the company improve. Businesses should also look out for employees who game the system, interfering with survey results by pushing customers to give positive answers.

Break down survey results: Companies don’t measure profit at only the corporate level; they break it down by product line, geographic region and so on. Granular performance measurements enable teams to make better decisions and be accountable for results. Enterprise Rent-A-Car, for example, uses a measure of customer loyalty that it calls ESQi and applies it to individual rental locations. The specificity of the data encourages employees to be more responsive to customer feedback.

Validate survey results: Ongoing analysis of retention, purchasing patterns and referrals can confirm the integrity of your feedback process. Establishing links between Net Promoter scores and business results will indicate that the scores are reliable.

Companies like Schwab understand that it is not the scores themselves but the behaviors they measure that produce growth. Net Promoter is valuable only when the scores accurately reflect the quality of customer relationships. But when companies take these steps to make sure the scores are reliable, and individuals in the organization know they can trust the metric, Net Promoter system becomes a powerful way to build and strengthen the relationships that result in growth.

Fred Reichheld is a Fellow and Rob Markey is a partner at Bain & Company. They are authors of the bestseller The Ultimate Question 2.0: How Net Promoter Companies Thrive in a Customer-Driven World.