Recognizing individual needs and customer preferences is key to succeeding and increasing competitiveness in both the commercial and public sectors. In the public sector, this is one of the ways to increase the efficiency of public funds allocated to public libraries. However, in order to make the right decisions, library management needs quality information about preferences and consumer behaviour, even from customers who cannot be the subject of routine research due to their young age. Therefore, this article proposes a new methodology for surveying children in order to design library services. The proposed methodology, which integrates principles from ethnographic and sociological methods, aims to overcome the problems of conventional sociological methods, such as how to conceive a child as a respondent and how to determine their preferences from hypothetical situations. This article uses a specially designed questionnaire tool to identify preferences, behaviour and information from children (as visitors of a library). The authors learned that Czech children went to the library primarily for books and games. In addition, the data from the questionnaire revealed patterns in the children’s and adults’ behaviour when visiting the library. All of the data in this article can be used for further research into consumer behaviour.