A common method is to "research backwards" in building a questionnaire by first determining the information sought (i.e., Brand A is more/less preferred by "x%" of the sample vs. Brand B, and "y%" vs. Brand C), then being certain to ask all the needed questions to obtain the metrics for the report. Unneeded questions should be avoided, as they are an expense to the researcher and an unwelcome imposition on the respondents. All questions should contribute to the objective(s) of the research.