Face-to-face household surveys sometimes ask field interviewers to record observations about selected characteristics of all sampled housing units. Some surveys ask interviewers to record judgments about potential respondents to serve as proxy measures of key variables. Past studies have shown that these judgments are prone to error, which has negative implications for survey estimators in terms of the bias and variance introduced by nonresponse adjustments based on the judgments. Practical techniques for reducing these errors are therefore needed. This article analyzes an intervention implemented in the 2006–2010 National Survey of Family Growth. The intervention was designed to provide field interviewers with observable predictors of a key auxiliary variable for which they were recording observations. The analysis shows evidence of a significant improvement in the quality of the observations. The article concludes with a discussion of directions for future work in this area.